1. It'd be interesting to hear a podcast on personal development as a topic on its own -- commentary along the lines of
http://www.stevepavlina.com/blog/200...-help-junkies/ and
http://www.stevepavlina.com/blog/200...f-help-cynics/ Or, e.g. the general approach to personal development as in podcast 1.
2. Human interactions, social development, etc. As in
http://www.stevepavlina.com/blog/200...relationships/ and
http://www.stevepavlina.com/blog/200...relationships/.
3. Analogies always work well in audio.
http://www.stevepavlina.com/blog/200...ultimate-game/ or something like it would make for a fun podcast.
4. Overcoming addiction -- TV, net or otherwise. e.g.
http://www.stevepavlina.com/blog/200...ews-addiction/
5. Consciousness, as in
http://www.stevepavlina.com/blog/200...ore-conscious/ ,
http://www.stevepavlina.com/blog/200...ore-conscious/ and
http://www.stevepavlina.com/blog/200...ss-revolution/. I've always enjoyed the consciousness approach to PD. It doesn't seem like you've approached the topic directly in any podcasts.