I'm a total podcast junkie (try doing PCR in a dead-silent lab for two years, then winning an iPod shuffle, and see if you don't turn addict). But finding new podcasts when you've exhausted an archive or ten is not as simple as giving your favorites five stars on Amazon or Netflix and seeing what they recommend. My old "system" to find new podcasts basically added up to Googling combinations of my favorites to see what else came up (zip), combing through all the most-dugg podcasts on Digg, and scouring the last.fm artists of other big NPR listeners.
The last.fm method gives pretty good recommendations, but it's slow. Podcast Finder speeds it up by using a database (fairly small right now) of last.fm favorites. As with all my little projects, there's room for improvement, but if you're a podcast fan, I'd love for you to give it a try. If I'm missing your favorite (or you have any other feedback), feel free to leave me a comment here.