Ok, once you can make a podcast and make an RSS document it, where do you put it?
You can figure lots of stuff out with an angelfire account, but at 20 mb, you will max that out pretty quick.
Most of the other options will require you to pay some money.
Here are a few links of businesses that provide the service.
Podcast Alley forum on hosting:
http://www.podcastalley.com/forum/viewtopic.php?t=4546