Audacity is free and has about 80% of the functionality of alot of the other programs that cost $100+. So, for the amateur, it's really the best way to go.
Garageband has alot of the same functionality, and comes free with Macs.
Here are some other free alternatives, but you'll find Audacity is the best one unless you want to step up to the next level of pay programs:
http://www.hongkiat.com/blog/25-free-di ... o-editors/