For those jumping into the digital age this something that you could do very easily for your students. A podcast is just an audio broadcast on the Internet. A good service to develop a pod cast is called Gcast and it allows you to make a broadcast right from your own home phone. This service allows you to review daily lectures, homework assigments etc.. Furthermore it develops a code that allows you to review things and leave a broadcast on your blog. Great for lectures, book readings etc..
http://www.podcastingnews.com/2009/02/20/why-go-to-class-at-all-lecture-podcast-listeners-outperform-class-attendees/
Greg
