I have been accessing Radio National podcasts for years. There is an incredible wealth of material available and although some programs are too long to be used in their entirety with students, it is easy to focus in on relevant elements. By adding RSS feeds, these are particularly helpful for senior students, in Biology, Modern History and Economics. They have access to material which is authoritative, current and interesting. Although it is not necessary to have an mp3 player, the portability of this medium allows for access when walking the dog or sitting in the car.
The quality of some podcasts for students needs to be checked (as for all resources).
Students love making their own podcasts and software like audacity makes this a simple process and readily accessible.