best. avatar. ever.
i'm guessing if you think moby is ambient you haven't heard the classics
eno's on land is _the_ seminal work. the rest of the ambient series is also quite good, most notably music for airports. another green world might qualify as ambient to you too. regardless, these records are the cornerstone of our modern world.
the other pillar of ambient is rdj aka aphex twin. selected ambient works II is one of the five greatest records ever made. SAW 1 is also ridiculously great. melodies from mars, analogue bubblebath 1 and 2, hangable auto bulb, etc. etc.
that's what i'm coming up with off the top of my head. tara jane o neil is someone more recent that i would classify as near-ambient, but her noise experiments and songs are more structured than true ambient (SAW 1 is heavily structured as well). i haven't really been following electronic as well as maybe i should, so i'm not sure what i could tell you about recent work in that...