Audacity 1.3.4 (beta) have been released. It’s in beta because it doesn’t include complete documentation and translations into other languages. Audacity is a multi-platform audio editor (Windows, OS X and Linux) and is absolutely free. Certainly something to check out if you haven’t got a proper audio editor for your podcasting purposes just yet.
Here is an e-book focusing on just that – podcasts with Audacity. I have no idea if it’s any good, but it could very well be worth checking out. Don’t believe all the hype on that page though (Audacity is not “universally recognized” as the number one software for podcasts).