One of the biggest frustrations of people who record and edit audio is the amount of time it takes to fix volume level issues. If you record two people, one of them is invariably softer than the other in the mix.
To solve this common frustration, Gigavox created The Levelator. Essentially, the software examines a WAV or AIFF file, looks for volume inconsistencies and fixes them.
The Levelator handles both the gain optimization on a file and RMS normalization to make sure the volume level is consistent. The output is a new file, so you can always go back to the original if you need to. The software runs on both Windows and OS X and is free for personal non-commercial use.
While The Levelator can’t do anything to make your podcast more interesting, this is the first tool I’ve ever seen that makes almost anyone sound like they hired a top-notch engineer.