Don McAlister has a full tutorial on that in the "Extra!" (i.e. paid) section of his outstanding Screencasts Online site. It might be a while before you see that content for free.
Nevertheless, creating podcasts with Garageband 3 (the one in iLife '06) is relatively simple. Chose the menu option to make a podcast, select the Female voice "instrument" (be sure to select "Real Instrument"), click the record button and talk.
You can add music tracks from iTunes just by importing them. Get royalty-free tracks from Apple's freeplay collection (download from .Mac) or the Podsafe Music Network (http://music.podshow.com/).
With respect to mikes, don't go for the extremely cheap or the extremely expensive. You can look up the MacWeek podcast; episode 04 is a tutorial on microphones for podcasting. I use a USB mic and it works fine. Setting the boom properly is important so as to avoid explosive "P's" and "B's".
Hi,
being new to the world of audio, I would love to see a module on how to create a great sounding podcast using Garage band and reasonably priced, simple-to-use audio equipment.
Questions I would have include what settings would be best, how to sound natural, what jingles to choose and finally, how to edit the audio once it is recorded.
Thanks!
clara the cat