The Levelator is an interesting (and free) software that adjusts the audio levels within a podcast for volume differences between the host and guests.
You used to have to go into audio software and manually turn down your overzealous guest number one, who ate the mic for the whole interview, and turn up your soft spoken guest number two, so you could tell what the heck he was saying. Now, you can drop your raw audio file into The Levelator, and it pops out a new version with the software's best guess on all those audio level fix-ups.
The Levelator runs on Windows, OS X (universal binary), or Linux (Ubuntu), and comes as a free download from The Conversations Network. I've run a few tests, and seen fairly good results. I'm interested in seeing what other people's experiences with it are.