Listing of some fun filled websites

bored.com
Bored - Links to the most fun and interesting sites on the Internet. When you have nothing better to do, visit Bored.com.
newgrounds.com
New Grounds - A huge website with lost of fun flash games, movies, and more!
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.
zipperfish.com
Zipper Fish - Fun flash games, quizzes, and articles.
flash-game.net
Flash Games.net - an archive of flash games
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.