I use two main programs to record or edit my audio files. Once you've finished recording or editing sound, both programs allow you to export your audio file and use it however you like (listening to it on iTunes, creating a movie soundtrack, making sound art, etc.)
Audacity
Audacity is a program that records and edits sound. It's simple to use, and you can download it for free at
http://audacity.sourceforge.net/. The only advantage that it has over GarageBand is that you can export your finished audio file in any format you want (including formats that are compatible with Windows and PCs).
GarageBand
GarageBand is included in Apple's iLife package. The advantage that it has over Audacity is that it already includes rhythms and beats in order to make your own tracks. These can then be combined with your own recorded audio.
