This should cover a bunch of different Ambient styles, but all of the artists are absolutely fantastic and worth digging into. I'm definitely leaving out a fuckload more, but there are a ton of great suggestions in the other responses, too. Happy listening! :D
Biosphere
Ryuichi Sakamoto
Loscil
A Strangely Isolated Place (record label & mix series)
Silent Season (record label)
Kelly Moran
Rafael Anton Irisarri
Harold Budd
Steve Roach
Terre Thaemlitz
Gel-Sol
Koss
Nils Frahm
FAX Records
Pete Namlook
Hiroshi Yoshimura
Benoit Pioulard
Carlos Nino
Woob (particularly woob1194)
ASC
Autumn of Communion
Wanderwelle
Celer
Christina Vantzou
Julianna Barwick
Mary Lattimore
Grouper
Suzanne Ciani
MPU101
Deru
Lusine (Language Barrier in particular, his only full-Ambient album)
Nice list. I would second Ryuichi Sakamoto, Loscil, Julianna Barwick, Mary Lattimore, and Grouper for sure and there are lots of other good ones on there.
I'd add Windy & Carl, A Winged Victory for the Sullen, Yui Odonera (lots from the Serein label actually), Max Richter, and most of all Stars of the Lid.
The Disintegration Loops is lovely and I found it very thought-provoking. The concept of hearing the medium being destroyed, in this sort of breathing / heartbeat / day and night cycle, is a very powerful way to think about mortality.
One of the tracks still sounds like you're hearing someone drowning over the course of 17 minutes and it's terrifying. It's the first track here, though I believe they are named / ordered incorrectly. Just comparing 2 minutes in vs 15 minutes.. it still creeps me out.
