Huge fan of ambient (especially psybient) and in my opinion these are some of the highest quality musicians in the genre:

Carbon Based Lifeforms

Tipper

Solar Fields

Ishq

Stellardrone

Cell

Aes Dana

Brian Eno

Sonus Lab

Aphex Twin

Biosphere

Koan

Ott

Shpongle (not quite ambient but seriously)

There are so many other great producers I can't think of..