Audacity is a GREAT program and I endorse it as well. Right now it is the only audio editing program I use, for clients and also for my podcast.
It is easy to use too. There are many things you can do with the program like Tess already mentioned. I like the fact that you can increase or decrease the sound, add fade ins/out and save as either a .wav or .mp3. For a free program there really is a lot of functionality.
I recently purchased a microphone that came with audio editing/recording software. I played around with the new software a bit, but most definately prefer to use Audacity.
