A lot of people, actually. Not only are they podcasting in their classes, but they are blogging about podcasting in their classes and podcasting about podcasting in education. The beauty of making material available to your students via podcasts that they are able to take class content with them on a portable device if they choose, replay lectures, or even create their own podcasts and share them with the rest class and/or the rest of the internet.
See what is going on:

• Podcasts of the Museum of Modern Art by students of Merrymount Manhattan College – http://mod.blogs.com/art_mobs/
• Third graders podcasting – http://bobsprankle.com/blog/C1697218367/index.html
• Teaching Russian via podcast – http://spoonfulofrussian.com/
• Podcasting from the Kuskoquim Campus – http://community.uaf.edu/~kuc/blog/archives/podcasts
  (more about what they are doing in Nunivak)
  

Getting your own podcast started takes just a little curiosity, access to a computer with a mic, and Audacity – free software that you can use to prep your recordings for your listeners. You will also need the LAME MP3 encoder to save your audio to MP3.

Tutorial on podcasting using audacity http://software.newsforge.com/article.pl?sid=06/03/17/1633214&from=rss

You can also download sounds tracks that are available for use on your podcasts that are open under Creative Commons Licensing at places like ccMixter.com.