I think Drunken Gamers is the closest to Idle Thumbs as far as being genuinely funny. They are pretty old school though, which I love, but others might not. Every March they do Shmupreciation month, again something I love about them. I can see how Thumbs listeners would be much more PC-centric, though. Giantbomb has recently been doing more PC stuff, but they're still a console podcast. So, I'm really down to DGR and Giantbomb now. I've tried some of the IGN podcasts; Gamescoop and Three Red Lights are ok, but they don't fill the void of Idle Thumbs. The Mobcast at Bitmob can be very good, but it really depends on who the guests are. When Robert Ashley was around, they were top notch.
For a non-gaming cast that might interest you, I love Neil DeGrasse Tyson's Star Talk and has already been mentioned Atheist News.