I've been listening to .NET Rocks for quite a while now. They almost always have good content, and the production value is insanely good. I had problems when they went away from AAC feeds (note: it looks like the AAC feed is back again!) where the entire episode would restart when I would bring my iPod out of a long sleep.

I've also been listening to more audio books as a way to kill time in the car. Most audio books are coming in as mp3, but then you don't get the benefit of speed-up playback or having the iPod remember your position. In order to have iTunes classify a file as an Audiobook, you need to do 1 of the following things:

1. Rip the audio file as AAC rather than mp3 (or convert an existing mp3 file to AAC using iTunes). Afterwards, rename the file extension to .m4b. The default extension for AAC encoding is .m4a, so you need to rename them manually.
2. On Windows, use this free software to do all of the work in one step.
3. On a Macintosh, use this script to do the work for you.