Podcasting is similar to the old radio shows -- it's audio only. If you add video, then it's vidcasting.
You can do a single project or a continuous one like Radio WillowWeb below. One wonderful use is to podcast your students reading progress.

You can use RSS to subscribe to podcasts about all types of information for education or enjoyment purposes. You can hear podcasts on your phones, iPods, mp3 players or on iTunes or simply on your websites.

All that is required is a great idea, a good microphone, a creative script, fade-in and fade-out music, sound effects if desired, and Audacity or an online podcasting site. You can make it as easy or as complicated as you like.

Download a great helpful booklet on podcasting: http://learninginhand.com/podcasting/booklet.html This booklet uses Audacity -- a free piece of software that can be installed on your computer. http://audacity.sourceforge.net/download/

More Into: The Education Podcast Network - Landmark Project - http://epnweb.org/

You can also use an online podcasting service (no need for software download) such as:

Some of the best:
Radio WillowWeb (Willowdate ELementary School) http://mps.wes.schoolfusion.us/modules/cms/pages.phtml?sessionid=cc17faa3b4b3cc4b4356056651b975f8&pageid=115312&sessionid=cc17faa3b4b3cc4b4356056651b975f8
Mr. Mayo's Podcast page - grammar hiphops and raps - http://mrmayo.typepad.com/podcasts/