An excellent way to promote your podcast for free is getting free exposure in the press. Podcasting is currently a very newsworthy topic. If you have an interesting angle or story to pitch, write up a quick press release and submit it to PRWeb. If the story is strong enough, you could get further press exposure for you podcast. This generates traffic and more listeners.
February is podcast month at PRWeb. Every morning they are selecting five podcast-related press releases to upgrade them to the $200 distribution level giving you increased exposure.
You have just under a week to take advantage of this. Has your podcast done something of interest recently? Then flaunt it! Write up a quick release and send it on in. Even after February, basic submissions to PRWeb will still be free and worth your time.