Audacity - Free + open source recording and editing software, suitable for voice recording.
Garageband - Free on Mac OSX. Record and produce music.
Reaper - Reaper is a fully functioning Digital Audio Workstation. Download the 60-day evaluation trial for free. Preferable to Audacity for multitrack musical or audio recordings. Includes audio and MIDI tracks, as well as digital instruments and effects, and support for VST and AU plugins.