Podcasting is a great way to spread the word about the work that you do. Try finding a blogger who writes about the kind of stuff you write about and approach them about a possible interview. Bloggers are always looking for good material.
Another thing you can try is posting podcasts on your own blog. Perhaps create a series of podcasts covering a subject from your book, or post chapters from your book as podcasts.
I did a few interviews for the M-Word while at Comic Con. Check out this podcast with 100 Days of Monsters author Stefan Bucher. Stefan shares his thoughts on the con and talks about his own favorite comics. (*for these interviews I used a simple hand-held digital voice recorder that I picked up at Office Depot… totally guerilla style…)