Barry Bloye wrote:

Compression, compression, compression!

Dunno how versed you are in recording technique, but it's vital to get good levels in your audio. Do a soundcheck and set the initial input level as high as you can without it clipping, and then turn it down another notch to leave some extra headroom -- you'll inevitably get louder as you get more in to the discussion!

After you've finished recording, use a compressor plug-in to smooth out the peaks in your recording, and this will in turn let you raise the overall level.

I've found quite a few podcasts unlistenable because they've been quiet recordings punctuated with sudden peaks, which some liberal compression could have fixed -- doesn't make for comfortable iPod listening on the bus.