http://www.bored.com

Bored – Links to the most fun and interesting sites on the Internet. When you have nothing better to do, visit Bored.com.

http://www.newgrounds.com

New Grounds – A huge website with lost of fun flash games, movies, and more!

http://www.ndtoday.com/games

ND Today Games – Fun flash games run by Notra Dame University. As it is run by a university, most school and work networks won’t block it.

http://www.zipperfish.com

Zipper Fish – Fun flash games, quizzes, and articles.

http://www.flash-game.net

Flash Games.net – an archive of flash games

http://www.aaafunnyvideos.com

Funny Videos – A free site full of hilarious videos.

I think YouTube / Google Video are also great sites to visit to find a lot of funstuffs.