YouTube
About 300 hours of content is uploaded to YouTube every minute. It's now offering an ad-free subscription service. Reuters

Who hasn't used YouTube? Alexa ranks it just behind Google and Facebook as the third-most-visited site in the U.S. while Quantcast has the video-sharing site second behind Google. YouTube seemed like a great bet when it was founded in 2005 and Google quickly purchased the site in 2006. So, let's thank Steve Chen, Chad Hurley and Jawed Karim for YouTube and the countless videos that have been shared and gone viral.

Karim had the honor of uploading the first video, "Me at the Zoo," posted on April 23, 2005 -- and, well, it's still kind of terrible. It's the only video Karim posted under the username Jawed. It has accumulated around 19.8 million views and runs 19 seconds. In it, Karim is standing in front of elephants at the San Diego Zoo. "Cool thing about these guys is that they have really, really, really, um, long trunks and that's cool," Karim says to the camera.

Since Karim uploaded "Me at the Zoo," YouTube has added more than 1 billion users; 300 hours of content is uploaded every minute on the site. As for the most-viewed videos of all time, Psy remains king: "Gangnam Style" has more than 2.3 billion views and more than 5 million comments. Justin Bieber's "Baby" is the second-most-viewed YouTube video of all time with more than 1.1 billion views. Katy Perry occupies the third and fourth spots -- for "Dark Horse" and "Roar," respectively -- while LMFAO's "Party Rock Anthem" is the fifth-most-viewed video on YouTube.

Music dominates the top 100 videos on YouTube. The only viral video to crack the top 30 is "Charlie Bit My Finger -- Again!" The video, uploaded by HDCYT, has more than 800 million views and is one of the few nonmusic videos in the top 100.

Happy birthday, YouTube!