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YouTube users watch more than 2 billion videos per day.

AOL Instant Messenger introduced instant messaging to the masses, and helped AOL rise to early dominance in the computing field.

Flickr said it hosted more than 3.6 billion pictures as of 2009.

Within the first month of its launch, more than half of the Harvard student body joined Facebook.

As of 2011, Twitter users send 6.5 million tweets of 140 characters or less every day.

After its 2003 introduction, MySpace quickly became the world's largest social networking site, hitting that mark by 2006.

NASA astronaut T.J. Creamer sent the first tweet from space in 2010.

In 1971, researchers sent the first e-mail. The sending and receiving computers sat side by side in the same room.

Facebook opened its doors to nonstudents in 2006, and just two years later, it became the largest social media site in the world.

The first public version of MySpace was launched in 2003 after only 10 days of work by its developers. It was designed to compete with Friendster.

Facebook dominates the social networking market, but social gaming site Friendster gained 3 million members after its 2002 launch and maintains 90 million members as of 2010.

Though not as popular as Facebook or MySpace, Orkut claims 100 million members as of 2010, most of them in countries such as Brazil; the site never really caught on in the United States. In 2011, Google announced the launch of Google+ and early research showed it attracted young, male and educated adopters.

Club Penguin allows kids to interact online, but limits their ability to share personal information with strangers.

Launched in 1994, Geocities had more than 1 million members by 1997.

LinkedIn serves as the social network for the business world, allowing users to share resume and job information; it's also the second largest social network. Facebook still reigns as the top site, with more than 160 million users.