This post is your one-stop shop for everything you need to know about today’s Yuri’s Night’s goings-on. Read on for all the details:

Today is the biggest day in the history of celebrating space exploration.

On April 12, 2011, the 50th anniversary of Yuri Gagarin’s first human spaceflight and the 30th anniversary of the launch of the first Space Shuttle, Yuri’s Night is throwing over 500 parties and events around the world to commemorate our history in space and build towards a future of humanity on the Moon, Mars, and beyond. Hundreds of thousands of people are celebrating by watching our Global Webcast, entering space vacation contests, sharing pictures of their local events with the world, downloading free e-books, and meeting up in local museums, clubs, bars, backyards, schools, and observatories to learn about space–and have fun doing it.

“Everyone from Google to the Los Angeles Times is making note of this historical landmark, and I’m thrilled to see how excited people around the world are to celebrate the spirit of exploration and discovery that Yuri Gagarin embodied,” said Assistant Director Brice Russ. “Whether your nearest Yuri’s Night event is down the street or a hundred miles away, there’s something you can do to participate.”

As of 12 PM Eastern Time on 4/12, there were over 530 registered Yuri’s Night events in 74 countries on all 7 continents (including, for the second year in a row, the South Pole). Among these parties are:

Yuri’s Night Los Angeles, the home of the first flagship YN event in 2001. Yuri’s Night co-founders George and Loretta Whitesides will be joining celebrities and hundreds of space fans to talk about Yuri’s flight and the importance and awesomeness of space at LA’s Griffith Observatory.

Yuri’s Night Tokyo: despite the devastation of the recent tsunami in Japan, Yasuharu Kawabata and others are still meeting to celebrate Yuri’s Night with food and drink at the ALICE Aqua Garden in Chiyoda. All proceeds from party admission will be going to disaster relief efforts.

Yuri’s Night Moscow: the Russian capital has six YN celebrations this year, not least of them the one being held by the Mars500 crew, an ESA project simulating the challenges of a manned Martian spaceflight. A greeting to YN from Mars500 is available online.

On the global level, Yuri’s Night is running three contests: the “Call to Humanity” Space Ad Contest, which calls on participants to create a print ad with the goal of inspiring public interest in space; the Global Space Sweepstakes, completely free to enter in countries around the world, and the OpenLuna Video Contest, where video editors are challenged to use Yuri’s Night’s extensive video resources to create a promotional segment for YN. The first two contests have grand prizes of space-themed vacations to Russia (including microgravity flights and Soyuz rocket launches) provided by Space Travellers and valued at $9,000 each; the final contest has a $500 cash prize. All deadlines are April 15.

For the second straight year, Yuri’s Night is partnering with the acclaimed weekly program Spacevidcast to host a YN Global Webcast (at www.spacevidcast.com) running from this evening until the wee hours of Wednesday. Ben and Cariann Higginbotham will be checking in with over two dozen parties around the globe, from Havre, Montana to Kuala Lumpur. Andrew Kessler will be on the show to give away one million e-book copies of his Martian Summer, and the SVC team will be showing clips of Yuri’s Night greetings and interviews by everyone from Bill Nye, the Science Guy to the Expedition 27 crew of the International Space Station.

Yuri’s Night is partnering with many groups and organizations. YN has teamed up with Posterous to host Yuri’s Night Live (http://live.yurisnight.net/), a website that anyone can post YN pictures, videos and links to by simply emailing submit2@yurisnight.net. Yuri’s Night is also partnering with First Orbit to premiere their film, a recreation of the view from Yuri Gagarin’s flight using footage from the International Space Station and elsewhere, and is affiliated with Yuri’s Night celebrators such as YuriGagarin50, the X PRIZE Foundation and the Space Generation Advisory Council.

Yuri’s Night would like to thank Richard Garriott, Dave Masten, the Musk Foundation, our other sponsors and partners, and everyone around the world who’s helping to celebrate 50 years of human spaceflight.

For the latest YN news, keep visiting our Yuri’s Night Blog, Facebook and Twitter pages. Rock The Planet!