Audacity is probably the best FREE audio-editing program that I've ever used. It's easy to downlaod and, after a few minutes of experimenting with it, can be used to make simple adjustments to an audio track. It also has everything you need to to make more complex adjustments and it doesn't take very long to learn how to use the various tools.
What I use it for: Converting WAV files to MP3 files (unfortunately, it won't convert WMA files to MP3's), and editing audio files to use on other programs (such as Windows Movie Maker).
Tutorials: Christina and myself have created a couple of tutorials for those that want to use Audacity and need help getting started. Audacity 101 goes over how to download the program, Audacity 102 goes over how to upload and export audio files, and Audacity 103 goes over how to use some of the simplest editing tools on the program. These tutorials and other videos and links can be found on the right side of the blog under the 'audio links' header.
Things To Keep in Mind: One of the funny 'quirks' of Audacity is that the program will ask you to save a small file called 'LAME MP3 encoder' from a website the first time you try to save an audio file as am MP3. This is only a one-time thing and you can even delete the file after Audacity has used it once. There is a link to the download page under the 'audio links'.
