Audacity
Audacity is an user-friendly, free & open source audio editor. It is currently available for almost all operating systems, including Windows, Mac OS X, GNU/Linux and others. The software gets great reviews and ranks up there with some of the best in it's genre because of it's "clean interface, excellent features, and support for 32-bit floating-point audio" (and a great price - FREE! - if I may add). With Audacity, you can easily record/import audio, edit the files, add effects, and export to your desired file format.