Writing Excuses", "Sword and Laser", and "The Secrets". The "Chillpak Hollywood Hour" is also an occasional favorite. There are a handful of podcasts that I linked to from other sites, or that were otherwise recommended to me, but the style of those 'casts just didn't work for me so I never went back. Here's my advice to anybody thinking about doing a podcast.
1. If there are two or more people in the podcast, please try to keep it from
getting jokey and do NOT talk over each other. I find that "drive-time
radio jokey duo" style of 'casting the equivalent of nails on a
blackboard. Also be careful of wandering off-topic, especially if this means inside jokes and nattering about personal stuff. Nobody cares but you guys, so save it for Off Air socializing.
2. Music: Snappy intro jingles are nice, but when it's all said and done I don't really care about any music you may or may not have as an intro or outro, I just care about what you have to say. A good, clean recording goes a long way toward keeping me engaged.
3. More musical mayhem: The jarring "are you paying attention?!" monkey-banging-on-a-drum riff. A news station local to me (KIRO 97.3) does this with their twice-an-hour traffic/weather reports, and it's really, really annoying, especially because of the heavy percussion. When I'm listening to late-night radio, the last thing I want is a sudden burst of obnoxious jazzy crap with a drum machine track that won't shut up.
4. Even more music whinging: The Ear Worm. Please don't feel compelled to run some noodley tune behind the whole podcast. Don't get me wrong. I love music. I've been known to play piano and harp. I run Pandora while I work on the computer, but that is music of my choosing, and there's a time and place for everything. When I'm listening to a podcast in my car, or over the racket in my kitchen, a music track under soft-spoken vocals is at best just distracting, at worst really annoying. That seemingly innocuous guitar jingle you've carefully edited into a loop to run behind your monologuing is auditory Chinese water torture (looking at you, Michael Stackpole...but your podcasts are still so worth my time that I'll keep listening, dang it).
I love being read to, and podcasts are a nice change from the audio books that I devour constantly. For me some are just plain entertainment, others a poor person's grad school. Keep 'em coming, just don't force me to listen to repetitive jingles while you deliver your words of wisdom. What you have to say is far more interesting to me.