I stumbled upon an excellent edublog recently and found that it contains some excellent info on RSS feeds. The blog is titles Techno Constructivist and it provides cutting-edge top-notch IT info. The entry that I linked to below contains a list of great RSS feeds (grouped by subject area).
And if you are in the market for just podcast here are 2 great places to find subject specific podcasts:
itunes.com (of course)