For me, MySpace has been a highly effective marketing tool. I use the MySpace search engine to find my target audience, friend them with an engaging "Hello come check out my Podcast", broadcast notices of upcoming episodes, and get (a little) listener feedback.
My MySpace page (http://www.myspace.com/nantekoto) now has over 400 friends and growing. For my needs, I sure can't beat the price (free). I just hope it stays around for longer than a Friendster minute.
Cheers, Michael Domingo, Host Nante Koto Dating Misadventures Podcast Washington, DC USA www.nantekoto.com