Apple Loops are brilliant. Sure, you can use them in generic
ways, pasting together music, but if you want them to act as raw
materials for remixing or mind-bendiningly experimental music (just add
effects), you can do that, too. And Mac sites keep releasing great
loops for free:

  • Free tune-up mini features sounds like "Space Bass" and "Rhodes Riff", 100 loops free as part of a promotion with
  • More exciting to me is iCompositions' new Drums on Demand loop library,
    with 90 drum loops, 19 "single hits", and 9 loop layers, also free.
    (Sorry, did you say something? I was busy mapping those single hits to
    the Simpler in Ableton Live.)

Windows users, you lose some of the elegant keywords in Apple Loops,
but any application that can read AIFF files can use them, too.

Check out iCompositions' loops section in their Tools guide for lots of free loop links.