Last winter, I bought myself one of the new core-duo Mac Minis.  I've found a lot of fun things to keep me busy, but none so much as GarageBand.  GarageBand is a multi-track recording studio in a box, complete with samples, sequencing, synthesizers, and effects, all within an easy to learn interface.  There's even a third party add-on hardware "mixing board" and controller called the iControl (shown here)

One of the coolest things I've seen in a long time comes from one of my favorite musical artists, Peter Gabriel.  Real World Remixed is a web site that's part blog, part podcast, and part music store.  Essentially, he's made available (for FREE!) zip files containing the individual recorded tracks of several songs from the Real World Records catalog.  GarageBand allows you to use the tracks to build your own remixes.  There's something very satisfying about hearing a song broken down to it's most basic parts.

Real World is his label, which is home to his own recordings and many other World artists like Afro Celt Sound System, Little Axe, Sheila Chandra, and more.  One of the first bundles available was Peter's own Shock the Monkey.  The site held a contest, judged by Peter himself, in which site members would submit their remixes using the bundled tracks.  There's some very interesting treatments.