Jason Calacanis just pointed to The Hype Machine, a free service which tracks MP3 blogs and builds a list of MP3 links that are downloadable by a podcatcher such as FeedStation.
Even better, they offer RSS feeds of their search results. If you’re using FeedDemon, simply perform a Hype Machine search from within FeedDemon’s browser, then click on FeedDemon’s autodiscovery icon after it lights up to subscribe to the search results.
Every item in the feed includes links to both Amazon and iTunes, where you can purchase the music (I’ve already purchased a CD I didn’t know existed thanks to the Amazon links). One big missing feature, though, is Creative Commons license information – it would be nice to see that added in the future.