As for actual scores/incidental music (music written for the film vs. songs chosen to fit it):
Crash (the Cronenberg film) - Howard Shore
Road to Perdition - Thomas Newman (one of the best new scorers around)
Lost Highway - Angelo Badalamenti
The Order - David Torn
Nosferatu - Popul Vuh (or Florian Fricke)
Though each of these guys has done other work I admire/enjoy as well, these top the list.
"Music is for fools, the future is prisons and math" - Alan Sparhawk