Hype Machine. There’s way too much music there to listen to it all, so I have iTunes set up to dip one track per hour out of the raging river, and delete each one after I’ve listened to it.
I also subscribe to podcasts for WFMU (for the 365 Days Project) and TMBG.
I don’t know if it’s on iTunes or not, but a friend of mine runs a regular podcast about gaming and game design… not computer gaming, but tabletop RPG and boardgames, as well as a bit about CCG games and the like.
If you’re a gaming geek, I highly recommend it. He’s had some pretty heavy hitters on the show, if you’re into independent gaming.