My favourite podcasts (in no order):
Games:
- G4 Web Series (Fresh Ink! is about comic books)
- IGN's Daily Fix
- Bungie Studios
- 343 (Halo)
- Irrational Games
Making Stuff
- The Ben Heck Show
- Make Magazine
- Backyard FX (part of Indy Mogul, I think)
- FilmRiot
Humour:
- The Onion News Radio/Video
- Some College Humor
- HowStuffWorks.com "Stuff they don't want you to know"
Writing:
- The Q&A with Jeff Goldsmith (formerly Creative Screenwriting)
- Writing Excuses
History:
- Hardcore History
- My History Can Beat up Your Politics
- Things you missed in History Class (Old episodes before Josh quit are very good)
Etc:
- Freakonomics Radio!!!*
- TekZilla
- Movie Trailers
I'm sure there are some good one's I'm forgetting.
Retired:
IGN Three Red Lights
1Up's L1sten Up (or whatever it's called now)
Official Lost
IGN's Tech Fetish
CheapyD, Wombat and Shipwreck (CAGcast, I think)
Also:
http://originaltrilogy.com/forum/topic.cfm/Podcasts/topic/11182/