My favorites at the moment are either early music, baroque (Bach, Rosenmuller or Vivaldi) or modern classical (John Adams, Arvo Pärt or Lou Harrison).
Except for Rosenmuller, this describes part of my collection. If you go for this, you might also find that early polyphonic plainchant is good for getting into (and staying in) the groove. The Hilliard Ensemble recording of the music of Perotin is outstanding.
Philip Glass: The "Heroes" Symphony, based on works by David Bowie and Brian Eno, also finds its way into the player at least once a week.
