Several good tutorials exist for those of you who want to review the basics or to delve into some of the more specialized functions.
Mindy McAdams, who teaches journalism at the University of Florida, created this one: http://www.jou.ufl.edu/faculty/mmcadams/tutorials/audacity_1/audacity_tute_1.html
Ironically, the audio cuts out at times, but I think you can get the gist of what she’s saying. The video pauses at the end of each “chapter,” so you have to keep clicking the play button.
Audacity itself has several tutorials for common tasks, such as editing audio files and mixing narration with background music. You can find links to those tutorials at: http://manual.audacityteam.org/o/man/tutorials.html