I look out for anything by Yoko Kanno or Taku Iwasaki. Choro Club also made some really fantastic relaxing music for the ARIA anime, and the second Yokohama Kaidashi Kikou OVA [which they worked on with Iwasaki, in fact].

Yasushi Ishii's soundtrack for the Hellsing TV series is fucking legendary, but he hasn't done any other material that I can find. I remember looking at his site and seeing only stuff about tap dancing [????].