Audacity is impressive, having both an intuitive interface and a host of features.

Audio can be imported in any of the following formats: WAV, AIFF, AU, IRCAM, MP3, OGG and MIDI.

Once imported the audio can be manipulated in all the ways you would expect, including cutting, copying, adding/removing silence, altering gain, and mixing tracks.

Various effects are available to spice up your recordings, ranging from simple amplification to wah-wah effects.

Multiple undo levels make a good base for experimentation, and the built-in amplitude envelope editor and spectrogram mode may prove useful.

It only has limited MIDI editing tools, but it does allow recording and editing audio in 16, 24 and 32-bit samples.

A selection of plugins are available, including LAME MP3 Encoder (allows Audacity to export to MP3 format), and VST Enabler (for loading VST plugins).