TED.com - Educational and inspiring. The most brilliant minds of the human race are all gathered there, and balances out the general idiocy of the typical crap we see on the internet.
cgtalk.com - Mostly because I'm a forum leader there and also teach an art workshop for them.
kvraudio.com - Because I'm a composer/sound designer and I love all things related to music-making, especially computer-based stuff.
V.I. Control - Same reason as KVR, except it focuses more on orchestral music and film/game scoring.
Penny Arcade - Because it makes me laugh and I'm an avid gamer.
I'll cheat and add one more--Facebook, and only because I live away from all of my family and friends, so this is the best way to keep in touch.