via CDM, NI have released a free soundpack for Kore Player (which is free also) or Kore 2.
There is also a 400MB free Live Pack from Ableton, and a few more from them here.
The Avant Garde Project is restoring old recordings of early electronic music, most of which are long out of print. Their collection includes compositions by some pretty famous composers ... or at least composers that you've read about in history books, even if you've never heard them. Reading down the list of composers, I see John Cage, Milton Babbitt, Pauline Oliveros, Morton Subotnick, Paul Hindemith and many others.via This Is Not A Label.