One is the Personal Growth Podcast Directory which specializes in, er, Personal Growth. The topic areas cover alternative health, spiritual development, motivation, emotional wellbeing, and more.
The index uses a single level hierarchy of topic categorization. In addition to the topic index they have a "tag" system to offer a second way to access and find podcasts.
The web site, well, maybe they're having a bad day today, but it seems rather flaky in that every other page I click on fails to load, but if I ask my web browser to reload then it loads correctly. I've given up trying to figure out this site since it's responsiveness is so bad.