Heres a free sound editor, the only problem is it's a single layer editor, but it's a good one. it will also convert files inbetween formats. (mp3 - Wav, and vice versa, also has quite a few other formats to save files too as well.) Major Geeks
This site is a great place to find freeware/shareware programs for just about any purpose. They also try to only post programs that dont have spyware hidden in them.Analog X
Heres also another great site, for those that want some original free programs. Lots of neat stuff here for those that love to tweak they're computer, as well as some great free software.