The coming election cycle will likely be the most expensive in history. Thanks to Citizens United and other recent court decisions, individuals, corporations and unions can make unlimited donations to so-called super PACs that support a candidate. The money is flowing in. So, exactly who is donating, and what do they want?

Here’s our guide to the top 10 super PAC contributors through Jan. 31, the latest date for which donors have been required to disclose. Unless otherwise noted, all estimates of net worth are from Forbes. (See our PAC Tracker for an interactive breakdown of all the money going to super PACs and others.)

Harold Simmons

Amount donated: $11.2 million (Contran, a company owned by Simmons, has donated $3 million.)

To whom: $10 million to American Crossroads, the Republican super PAC affiliated with Karl Rove; $1 million to Winning Our Future, the super PAC supporting Gingrich; $100,000 to Restoring Prosperity Fund, the super PAC supporting Rick Perry; and $100,000 to Restore Our Future, the super PAC supporting Mitt Romney

Net worth: $9.3 billion

Residence: Dallas

How he made his fortune: Buying and selling companies.

Background: Dubbed “Dallas’ most evil genius” by D Magazine, Simmons made waves in the Longhorn State a decade ago when his company, Waste Control Specialists, won permission to build a $500 million, low-level radioactive waste disposal site in West Texas. At the time, Simmons was Gov. Rick Perry's second-largest donor, having given $100,000 to Perry’s campaign 10 days after Perry signed legislation allowing WCS to accept low-level radioactive waste from outside Texas. Much of the waste WCS was cleaning up came from another Simmons company that had repeatedly been cited for environmental violations. A Simmons spokesman said at the time that concerns about the project were exaggerated.

On a personal note, Simmons has been sued by two of his daughters. In 1997, the daughters alleged that he had used trusts set up for them for his own purposes. They also claimed that Simmons had pressured them to make hundreds of thousands of dollars in campaign contributions from the funds. Two other daughters sided with Simmons, whom The New York Times called a “corporate version of King Lear.” The legal battle ended a year later when Simmons agreed to give his daughters $50 million each if they would relinquish claims to the rest of his fortune. Simmons denied all wrongdoing.

Sheldon and Miriam Adelson

Amount donated: $10 million (Adelson also reportedly contributed another $10 million in February, which doesn’t have to be disclosed until later this month.)

To whom: Winning Our Future, a super PAC that backs Newt Gingrich

Net worth: $21.5 billion

Residence: Las Vegas

How he made his fortune: Owns casinos and resorts.

Background: The Adelsons met on a blind date in 1989 and married two years later in Israel. The couple’s honeymoon to Venice inspired Sheldon Adelson to demolish his Las Vegas Sands casino in 1996 and replace it with The Venetian.

The Department of Justice and Securities and Exchange Commission have been investigating the Sands casinos on the Chinese territory of Macau for alleged bribery of foreign officials. Adelson said it is “not a serious case.”

Miriam Adelson is an Israeli physician specializing in drug addiction. (She and her husband fund a drug-treatment clinic in Las Vegas.) The Adelsons have contributed to Israeli foundations such as Yad Vashem, the Holocaust museum. Asked in January what Adelson will get out of his donations, Gingrich told an interviewer, “Well, he knows I’m very pro-Israel.” A 2008 New Yorker profile also offers an in-depth look at Adelson and his positions on Israel.

Bob Perry

Amount donated: $3.5 million

To whom: $2.5 million to American Crossroads, the Karl Rove super PAC, and $1 million to Restore Our Future, the super PAC supporting Mitt Romney

Net worth: Not available

Residence: Houston

How he made his fortune: Perry Homes, a homebuilding company

Background: The media-shy Perry (no relation to Rick) has been described as a “reclusive character” and rarely speaks with reporters. But while Perry may not talk, his money does. Perry, a longtime supporter of the Republican cause, was a major funder of the Swift Boat advertisements that in 2004 attacked Democratic presidential candidate and Sen. John Kerry. Perry also gave $7 million to American Crossroads in 2010.

Perry, who owns one of the nation’s largest homebuilding companies, was a major backer of the 2003 creation of the Texas Residential Construction Commission. One month after Perry gave $100,000 to Rick Perry’s re-election campaign, the governor appointed an executive at Bob Perry’s company to the commission’s board of directors. The body, meant to regulate the state’s homebuilding industry, was criticized as a tool of the industry because it circumvented the courts in disputes between homebuyers and homebuilders.

The commission was abolished in 2009 by the state legislature after a government watchdog concluded that “it is clear that the agency functions as a builder protection agency.”

Peter Thiel

Amount donated: $2.6 million

To whom: Endorse Liberty, a super PAC supporting Ron Paul

Net worth: $1.5 billion

Residence: San Francisco

How he made his fortune: Helped found PayPal, early investor in Facebook.

Background: The director of both a hedge fund and a venture-capital firm, Thiel has made much of his fortune investing in Internet startups. Thiel earned $55 million in 2002 alone when he and a friend decided to sell PayPal, which they had co-founded, to eBay. In 2004, Thiel gave $500,000 to Facebook, its first outside investment. He now owns 7 percent of the company and has a seat on the board.

As The New Yorker recently detailed, Thiel is kind of a pessimistic futurist who thinks the U.S. has fallen behind. “What happened to the future?” a page on his hedge fund’s website asks. Perry is also a libertarian and strong supporter of both unfettered capitalism and gay rights. According to the San Francisco Chronicle, Thiel hopes to build a libertarian movement in the United States and sees his contribution to Paul as the first step.

Jon Huntsman Sr.

Amount donated: $2.2 million

To whom: Our Destiny PAC, a super PAC supporting his son, Jon Huntsman

Net worth: $1 billion

Residence: Salt Lake City

How he made his fortune: Huntsman Corp., a chemical company

Background: Now most famous for being the father of a former presidential candidate, Huntsman Sr. is a self-made man who founded a huge corporation that markets and manufactures chemicals. The son of a rural schoolteacher, Huntsman actually expressed sympathy with the Occupy Wall Street movement. Instead of supporting more taxes for the rich, however, Huntsman believes the rich should be induced to donate their money to charity.

Huntsman is one of 19 billionaires who have given away at least $1 billion each. Huntsman has pledged to give away nearly his entire fortune. A profile of Huntsman in Forbes magazine reported that when he learned he had prostate cancer, he made three donations on the way to the hospital, giving $1 million each to a homeless shelter and a soup kitchen and $500,000 to the clinic that found his tumor. Huntsman is a four-time cancer survivor — he also has had oral cancer and skin cancer twice – and funds the Huntsman Cancer Institute at the University of Utah, which Jon Huntsman Jr. will chair now that his presidential bid is over.

A. Jerry Perenchio

Amount donated: $2 million, through his living trust

To whom: American Crossroads, the super PAC affiliated with Karl Rove

Net worth: $2.3 billion

Residence: Bel Air, Calif.

How he made his fortune: Former chairman and CEO of Hispanic TV network Univision

Background: The Los Angeles Times profiled Perenchio in 2006 as he was considering selling Univision, America’s largest Spanish-language network. The grandson of Italian immigrants, Perenchio grew up working in vineyards in Fresno, Calif. He got his start as a talent agent, orchestrating the legendary 1971 boxing match between Muhammad Ali and Joe Frazier, according to The Times. Perenchio is also credited with launching Elton John’s U.S. career. Later, Perenchio moved into the movie business and still owns the rights to “Blade Runner” and “Driving Miss Daisy.”

Perenchio is Malibu’s largest landowner, and his Beverly Hills estate borders that of Nancy Reagan. An alumnus of UCLA, Perenchio has donated more than $50 million to the university and other Los Angeles-area organizations such as the Walt Disney Concert Hall.

Perenchio was also a big supporter of Sen. John McCain’s 2008 presidential bid. He raised $172,000 for McCain that year.

Jeffrey Katzenberg

Amount donated: $2 million

To whom: Priorities USA Action, the super PAC supporting President Obama

Net worth: $1 billion in 2005

Residence: Beverly Hills, Calif.

How he made his fortune: Film producer and CEO of DreamWorks Animation, former chairman of Disney's film division

Background: This New York University dropout was chairman of Walt Disney Studios when it produced such hits such as "Beauty and the Beast," "The Little Mermaid," "Aladdin" and "The Lion King."

While at Disney, Katzenberg had a reputation for being hyper-controlling, telling employees “if you don’t come to work on Saturdays, don’t bother to come in on Sunday.” Katzenberg left the Magic Kingdom in 1994 after an unsuccessful bid to become company president. Upon leaving, Katzenberg sued the company for $250 million, saying he did not receive a fair share of profits. The suit was settled in 1997.

After leaving Disney, he teamed with David Geffen and Steven Spielberg to start DreamWorks SKG, with which he produced some of the biggest animated films of the last decade, including "Madagascar" and the "Shrek" series.

Katzenberg supported Obama in 2008, raising more than $1.7 million and calling his effort “the single easiest fundraising phone call that I have ever made, ever.”

Julian Robertson

Amount donated: $1.25 million

To whom: Restore Our Future, a super PAC supporting Mitt Romney

Net worth: $2.4 billion

Residence: New York City

How he made his fortune: Hedge funds

Background: Robertson has been celebrated as the “godfather of the hedge-fund industry.” Robertson founded Tiger Management in 1980. Named at the suggestion of one of his three young sons, it was known for its attention to detail — it once sent a commodity analyst to Bahia, Brazil, to estimate the number of coffee bushes being cultivated before betting that the commodity’s price would decline.

The firm lost big in 1998 after Robertson bet against the Internet. But he maintained his philanthropy. In September that year, he gave $25 million to New York City’s Lincoln Center, a month after he announced his fund had lost $600 million. Today, Robertson continues his giving at Duke University and the University of North Carolina-Chapel Hill.

Robertson has given small amounts to Republicans running for Senate, most recently donating $7,500 to Scott Brown, R-Mass. His foundation has contributed to medical research, including $10.2 million to Duke for stem-cell research.

Foster Friess

Amount donated: $1.15 million

To whom: $1 million to the Red White and Blue Fund, a super PAC supporting Rick Santorum; $100,000 to FreedomWorks for America, a super PAC opposing economic regulations; and $50,000 to Leaders for Families, a super PAC supporting Santorum

Net worth: $500 million, according to The Wall Street Journal

Residence: Jackson, Wyo.

How he made his fortune: Founder of Friess Associates

Background: Friess made headlines in February when, in an interview with MSNBC’s Andrea Mitchell, he entered the debate over health-care coverage for contraceptives.

“This contraceptive thing, my gosh, it’s so inexpensive,” he said. “Back in my days, they used Bayer aspirin for contraceptives. The gals put it between their knees, and it wasn't that costly." He later apologized, writing on his website that the remark was meant as a joke, which “bombed.”

Friess has been an unwavering supporter of Rick Santorum. At the end of January, when it looked as if Santorum might drop out of the race, Friess pledged his commitment to the candidate in an interview with CBS News. That same day, Friess appeared on Bloomberg TV, saying that if he had his way, Santorum would be president, with Mitt Romney “in charge of the entire economy.” He also suggested turning over “the keys of Air Force One to Herman Cain and let him fly around the world selling America.”

Robert Mercer

Amount donated: $1.1 million

To whom: $1 million to Restore Our Future, the super PAC supporting Mitt Romney, and $100,000 to Club for Growth Action, a super PAC that advocates limited government

Net worth: Not available

Residence: Long Island, N.Y.

How he made his fortune: co-CEO of hedge fund Renaissance Technologies

Background: This head of a $15 billion hedge fund made headlines in 2009 when he sued the builder of a model railroad installed in Mercer’s Long Island mansion. Mercer claimed he had been overcharged by almost $2 million. The model, which was completed in time for his daughter’s wedding, is half the size of a basketball court. The suit has yet to be decided.

Before becoming a hedge fund manager, Mercer worked at IBM on voice-recognition and translation programs. In October 2010, he donated $200,000 to Concerned Taxpayers of America, a super PAC that spent the money on ads attacking Democratic congressman Peter DeFazio in Oregon. Mercer was one of only two donors to the super PAC. The editorial board of The Oregonian used the donation as an example of the dangers of campaign finance, writing that “there’s something wrong with a campaign finance system that gives a couple of obscure millionaires the ability to so strongly influence a congressional race in a district they probably have never seen.”

Robert Rowling

Amount donated: $1.1 million

To whom: $1 million to American Crossroads, the Republican super PAC associated with Karl Rove, and $100,000 to Restore Our Future, the super PAC supporting Mitt Romney

Net worth: $4.7 billion

Residence: Dallas

How he made his fortune: Owns TRT Holdings, which includes Gold’s Gym.

Background: The previous time Rowling donated to American Crossroads, he got himself in hot water with the gay and lesbian community. Rowling gave $2 million to Karl Rove’s super PAC in 2010, reportedly angering one San Francisco gym owner enough to leave the Gold's franchise.

In addition to supporting conservative causes, Rowling has donated large sums to the University of Texas through his family foundation.