Audacity is one of the most popular cross-platform software packages for audio production. It is available on all library computers and can be downloaded for free at http://audacityteam.org.
Audacity developers and users also maintain a wiki that contains useful advice for users of all skill levels.
The following lynda.com tutorials--available to all Temple University affiliates--contain basic information for novice users, as well as more advanced techniques for troubleshooting common problems. Login using your AccessNetID and password.