1) Try songs by Earth, like:
[ame=http://www.youtube.com/watch?v=xYcQT8F58OU]YouTube - Earth - The Bees Made Honey in the Lion's Skull[/ame]
or
[ame=http://www.youtube.com/watch?v=LKT0vKI3W8Y&feature=related]YouTube - Earth - Omens And Portents II: Carrion Crow[/ame]
and really, just about anything else they did.
2) Pretty much the entire soundtrack for The Passion of the Christ by Peter Gabriel, like:
[ame=http://www.youtube.com/watch?v=D8Rro1EPLW4&feature=related]YouTube - Peter Gabriel 04 Lazarus Raised[/ame]
3) Vangelis' early work sometimes has a very moody feel to it, like this (poorly recorded) sample from his album, Soil Festivities:
[ame=http://www.youtube.com/watch?v=32UODtg41zc&feature=related]YouTube - Movement 2 - Vangelis[/ame]
4) Tangerine Dream's stuff goes in cycles as well, with some light stuff and moody stuff...check out Atem:
[ame=http://www.youtube.com/watch?v=Xnf-cvb3C1g]YouTube - Tangerine Dream - Atem [Edit][/ame]
5) Phillip Glass' Koyaanisqatsi has some nice stuff on it:
[ame=http://www.youtube.com/watch?v=LFBijDU8PpE]YouTube - Philip Glass - Koyaanisqatsi[/ame]
6) Surprising though it may be, industrial metal shredder Buckethead has also done some stuff that works for this. His work as Death Cube K is all sparse and atmospheric... and sometimes sinister, such as:
[ame=http://www.youtube.com/watch?v=khOLZ-qGzuo]YouTube - Death Cube K - Maggot Dream[/ame]
[ame=http://www.youtube.com/watch?v=aTl9qZPgPq8&feature=related]YouTube - Death Cube K - Thanatopsis[/ame]
[ame=http://www.youtube.com/watch?v=HqVulRYILFI&feature=related]YouTube - Death Cube K - Maps Of Impossible Worlds[/ame]