Good timing! Instructables has a step-by-step process for making a podcast. You can use this as a starting point if you are getting into podcasting for the first time to contribute to The 365 Days of Astronomy Podcast. There are also many other podcasting guides on the ‘net.
So fire up GarageBand or Audacity and start playing around!
Fame and fortune await.
I’ll also add that — if you submit your audio to this podcast, you don’t have to worry about the “publication” side of any of these how-to’s. We’ll be taking care of that part. We’d still encourage you to publish your own podcast as part of your experience with the 365 Days of Astronomy podcast so that if people enjoy your shows they can hear more.
Here is a Wikipedia list of free recording/editing software with supported operating systems given. Any of these, plus a microphone, and you’re almost done. Plus many laptops now have microphones built in.
http://en.wikipedia.org/wiki/Free_audio_software#Recording_and_editing
I’d recommend Audacity (or Garageband on the Mac), but it’s nice to know your options.
I’m assuming that MP3 is the format of choice here, though I haven’t found anything about audio formats yet. I can do MP4 just as easily, or even IFF if you’d like that better.