Download Squad points to FeedRinse:
If you’re trying to scrub a feed and filter it down in some manner, have a look at FeedRinse. This free web based service will let you import RSS feeds, set up some filtering rules, and it will spit out new feeds that you can subscribe to that give you your data after the filtering rules have been applied.
MacUser has a brief overview of Peel, an RSS reader for MP3 blogs.
Consider it what might happen if Dr. Frankenstein decided to marry NetNewsWire with iTunes. Subscribe to your favorite MP3 blogs, and easily skim a list of the music they post, adding the ones you like to iTunes and consigning those you don’t to a pit of everlasting torment. You can also stream music from webpages should you not be of the downloading persuasion.
While NetNewsWire allows me to keep up with various MP3 blogs, I can only download the MP3s. Of course, at $14.95, Peel is going to have to offer quite a few benefits other than streaming and downloading directly to iTunes before I’d consider it worthwhile.