http://cracked.com
A great comedy website, they have new content added every day with funny lists, videos, blog columns, and contests. Always manages to give me some laughs whenever I go there.
http://mega64.com
Awesome group of video game people, they make game videos and skits, sell their show on DVD along with merch and have a weekly podcast which I love.
http://xkcd.com
My favorite webcomic series, has a very specific brand of humor.
http://uncyclopedia.wikia.com/wiki/Main_Page
Funniest wiki on the web, period. Look up anything, there is some crazy article about it. Kind of like Wikipedia on crack.
http://ign.com
Great video game site, a very reliable place for news, videos, cheats, tricks, and reviews of games from all systems new and old.
http://wikipedia.org
If you want to know anything about anything, this is the place. The definitive sum of knowledge on the internet. I spend too much time on here. Warning: once you begin a wikipedia quest, you can end up following links for hours and hours...