mpc2aiff is a front-end interface for the command-line utility mppdec (by Frank Klemm), which will decode mpc files (musepack's mpeg plus; other supported extensions are "mpp" or "mp ") to aif format.
If you usually surf the web and share music, then you should know what is this format (or at least the mac-unplayable ".mpc" extension), a high quality compression algorithm based on MPEG.
mpc2aiff will convert these files to ".aif", suitable to burn to a CD or whatever other utility you give them (such as convert them to mp3).
NEW! Also, as for version 1.2, you can also encode wav files to mpc.
Reported at Versiontracker a way to play mpc files on your mac (under a Fink installation). Read it here!
The guy which compiled the a past version of mppdec (Etienne Petitjean) maybe is working in a plugin for iTunes, so you we'll be able, luckilly, to play these nativelly in our macs!