I've always been an Eno fan, but in the past 2 years have really expanded my Ambient catalog. Some of my favorite artists:
Eno - he has a lot out - everything in his catalog is worth having and most is even better than "Music for Airports"
Harold Budd - like everything I have by him
Frip and Eno - especially "Evening Star"
Michael Brook
John Foxx
Robin Guthrie - not totally ambient - some is a little more lively.
Klaus Schulze - more electronic, but ambient
Tangerine Dream - really more electronic, less ambient
Also - some Jazz "ambient" I like a lot:
Tord Gustavsen Trio - all of their catalog
Bobo Stenson Trio - Cantando, War Orphans
Ralph Towner and Gay Burton - "Matchbook"
Eno - he has a lot out - everything in his catalog is worth having and most is even better than "Music for Airports"
Harold Budd - like everything I have by him
Frip and Eno - especially "Evening Star"
Michael Brook
John Foxx
Robin Guthrie - not totally ambient - some is a little more lively.
Klaus Schulze - more electronic, but ambient
Tangerine Dream - really more electronic, less ambient
Also - some Jazz "ambient" I like a lot:
Tord Gustavsen Trio - all of their catalog
Bobo Stenson Trio - Cantando, War Orphans
Ralph Towner and Gay Burton - "Matchbook"