Audacity
Audacity rocks, for an free audio editor.
I use Audacity 1.3.3 (beta) for recording stuff for librivox.org .
It has performance improvements, a much improved "Noise Removal" tool, among other things, compared to v1.2.6. One thing it does lack is any documentation, so you might want to have a look around in
http://audacityteam.org/wiki/index.php?title=Main_Page or even download the 1.2.6 version, just for the help files, and then you can figure out the 1.3.3 (beta) version.
On my system (a Blue & White PowerMac G3 upgraded with a G4 processor running OS X v10.4.10) I was getting a few crashes at first with the beta version, but as near as I can make out, it had to do with double-clicking on a selection that crossed the border of a previously pasted-in section (as indicated by grey vertical lines). Now I'm just more careful when working in those regions, and double-clicking a selection is not supposed to do anything special anyway.
You will have to download and install a separate MP3 encoder to export projects to mp3 format, but it's pretty straight-forward. -
http://audacityteam.org/wiki/index.php?title=Lame_Installation
