There's a reason why Eric S. Raymond, in The Art of Unix Programming chose to use Audacity as a case study. It rocks. It is very easy to use, and gets its job done well.

Audacity is the kind of program that almost everybody needs: a simple "click the red button to record" sound editor. You'd think that OEM's would put software like this on their computers, since recording is one of those basic uses for their sound hardware. Unfortunately you're usually stuck with the Windows "sound recorder" app, with its restrictive limitations on sample length (max of one minute!).

Audacity can record as much sound as your hard drive can hold, and won't bog down doing it. It can also record multiple tracks and mix them together. It can export to OGG and MP3.

It's actually one of the better cross-platform Open Source applications. It's up there with Mozilla and Gimp.