Ambient? Oh Yes, Ambient Indeed.
First, some nearly beatless ambient - I go for the drifting, psychedelic end of the genre more than the creepy dark stuff - though I can agree that Biosphere's an absolute master.
Ishq - Orchid
Ishvara - Magik Square of the Sun
Brian Eno and Robert Fripp - The Equatorial Stars
Delerium - Spheres
Pete Namlook and Mixmaster Morris - Dreamfish (on the FAX label, home of more ambient, synth, and dub than l'll ever fully explore)
Robert Rich - Below Zero / Calling Down the Sky
Maitreya - Telluric Waves
Global Communication - 76:14
Ornament - Bleu
H.U.V.A. Network - Distances
Aphex Twin - Select Ambient Works Vol. II
Then, some not-quite-pure-ambient. Trance, dub, and downtempo with heavy ambient stylings:
Carbon Based Lifeforms - Hydroponic Garden / The Path (download here:
http://carbonbasedlifeforms.net/transfer/CBL_the_path.rar )
Solar Fields - Blue Moon Station / Leaving Home
Amorphous Androgynous - Tales of Ephidrina
Electric Skychurch - Sonic Diary
Future Sound of London - Lifeforms
Hesius Dome - Farewell Waltz
Mystery of the Yeti compilation
Infinity Project - Mystical Experiences
Shulman - In Search of a Meaningful Moment
Shpongle - Are You Shpongled?
Nodens Ictus - Spacelines
Saafi Brothers - Mystic Cigarettes / Midnight's Children
Spacetime Continuum - Sea Biscuit
Gus Till - Electric Oceans
Dub Trees - Nature Never Did Betray The Heart That Loved Her
That was fun to compile.