Albums in general, or artists? I'll do both.
You can't go wrong with any of these artists: Brian Eno (his ambient work, obviously), Harold Budd, Loscil, Gas, Monolake, Oval, Seefeel, Tim Hecker, Stars of the Lid, Jan Jelinek... there are a ton. I'd also recommend Bruce Haack, one of the most orginal artists of the last 50 years.
As far as albums to check out:
Gas - Pop
Brian Eno - Discreet Music & Ambient 1: Music for Airports
Oval - 94 Diskont
Seefeel - Quique
Jan Jelinek - Kosmischer Pitch & his work under Farben and Gramm
Tim Hecker - Radio Amor
Stars of the Lid - And Their Refinement of the Decline & The Tired Sounds of Stars of the Lid
Every album Harold Budd and Brian Eno worked on together.
You should also check out some Minimalist artists: Philip Glass, Steve Reich, Terry Riley, and Gavin Bryars.
Check out Solo Piano & Glassworks by Philip Glass for sure. You won't be disappointed.