I have made digital "podcasts" with my students using Garage band and found them to be a fantastic way to engage students. If I had more time, we would do ongoing podcasts but because they were "one-time" projects that I wanted parents to be able to see and hear, I played with the software so that all of our podcasts ended up on one page as entries and I blew away the "subscribe now" buttons before I posted them. The kids did an awesome job with their research and project creation.
I think it would be great to use podcasts so that students could review books for others; I may try to find a way to do that soon. Before I launch something like that, I want to make sure I have more ideas about management and time commitment in place.
Personally, I have found that podcasts are great for me when I miss an episode of a radio show I listen to, but I find that subscribing, unless it is for a show that is 5 minutes or less in length, is not worth it for me as I rarely go back and listen to missed episodes. Great for road trips though!!