some directories you can look in for feeds and often listen right on the site:
http://www.podcastingnews.com/forum/links.php
http://podfeed.net/
http://www.gigadial.net/public/
http://music.podshow.com/
http://www.podcastpickle.com/ (this directory is built into the Juice fetcher)
http://www.podcast.net/
http://www.podcastdirectory.com/
that should get you started.