Pinterest announced Wednesday that it began open registration, dropping its invite-only approach.

Users can now sign up for the social photo sharing website without waiting for an invitation, according to Pinterest's official blog. Now, prospective pinners can register using their email addresses, or log in with their Facebook or Twitter accounts.

"We're really excited to have the capacity to offer Pinterest to more people and if you're a Pinner with friends who've been waiting on the sidelines, we hope you'll let them know," the blog said.

Prior to opening up, users had to click "Request an Invite" on Pinterest.com, and enter their email address.

The California-based company announced in late July the addition of new categories, including, "Quotes," "Tattoos" and "Weddings," which joined old standbys, "Food and Drink," "Architecture" and "Home Decor." Some category names were tweaked: "Pets" became "Animals," and "Prints and Posters" is now "Illustrations and Posters."

Pinterest also reported that it had improved old categories, so users see less miscategorized pins as they peruse boards

The site, a virtual pinboard where members organize and share photos of their favorite things, is one of the fastest-growing social networks online. Reports suggest that Pinterest is the third-largest social network in the U.S., behind only Facebook and Twitter. It is currently looking to expand into overseas markets, such as France, Germany and Japan.

In May, Pinterest raised $100 million in a round of funding that values the company at $1.5 billion.

Will you sign up for Pinterest? Tell us in the comments below.