The recipe ones are up there, not least because they're rare episodes I can share with my mother. Probably my favorite vein is anything fundie-related, though, since I went through about four iterations of that in my childhood, including spending four years in a Baptist school before being kicked out for being Catholic. I can also share those with my mother, which, again, is a plus. By Demons Be Driven (Insane) is special to me because I snarked that site in days of yore and I'm glad to see it remains as crazy as ever.
For sheer recurring humor value, though, I always go back to the short with the "screenplay" about the slug woman. I listened to every episode of the podcast until the beginning of last year while working a library internship, and I was really good about keeping quiet no matter how funny it got, but "THAAAANK YOU" made me quietly collapse in the children's section and screech breathless laughter into the shelves. It STILL gets me when I think about it.