These are audiofiles that can be played on any MP3 player. You can connect to the site links and download either one of files or you can subscribe using RSS feeds or indeed through using iTunes. You can play them on your MP3 player, computer or audioplayer. The following are links to some really top Podcast sites:
General Science:
Nature
New Scientist
Philosophy Psychology:
All in the Mind
Philosophers Zone
General:
In our time