I like short stories and science fiction, so most of my podcasts are for that.
Escape Pod
Podcastle
Cory Doctorow's Craphound
Also, SpanishPod 101 for learning spanish. And Cody's Cuentos, which is a series of fairy tales in Spanish.
Podiobooks.com <- Burn, Shadowmagic, and Playing for Keeps have all been excellent.
I also like both of the They Might Be Giants podcasts. One is just music, generally about 20 minutes worth, and the other is a family/kids music video.
