I don't listen to many podcasts, I have to say. I've sampled a lot of them, but rarely come back to them. Here are the ones I do listen to fairly often.
1.) RPPR
2.) Return to Northmoor
3.) D&D Podcast (mostly the PvP/PA ones)
And that's about it. I occasionally listen to Order 66, but the guys there kind of tick me off and whenever they do, I stop listening for a long while. I keep wanting to listen to more of teh Penny Arcade ones, but I'm not on ITunes (I refuse to install Apple software) and can't find regular links off their sites.