Mira Calix on Warp's good. The first album's quite harsh, but strangely ambient with it, but Skimskitta (spelling?) the follow up has some quite beautiful melody's on it. It's not immediate, but subsequent listens are very rewarding. If you're familiar with Aphex and Autechre you'll know what to expect.
Boards of Canada's follow up to Music... is excellent.
Neotropic (girlfriend of Brian Dougans of FSOL) has some talent. Breaks, beats, downtempo jazz and at times industrial-sounding twisted ambient. 15 Levels of Magnification is ace, but it's worth tracking down the vinyl version as the tracklisting was completely different to the CD. Mr Brubaker's Strawberry Alarmclock was a decent follow up as was La Prochaine Fois (bad spelling day today

) both lean more towards a jazz stylee, but still very electronic.
DJ Spooky always impresses me, his Optometry album is very swirly jazz but he always leans back on his dub/hiphop roots. Songs of a Dead Dreamer (a few years old now) is very soundscapey with a lot of samples, cut-ups, and dubby sounds.
You can always rely on Biosphere for some decent ambient stuff. The earlier albums were more beat driven (Patashnik, Microgravity), things are more of a soundscape these days.
If you want some beautiful soundscapes try anything by Steve Roach or Robert Rich. Lustmord leans towards darker stuff, but also worth listening to.
A lot of what I listen to these days is dark "industrial ambient" - lots of pounding beats and weirdness. Iron Halo Device, Megaptera, Sleep Research Facility, Stone Glass Steel, Hazard, Techno Animal, Curse of the Golden Vampire, Lab Report, Kerovnian, A Challenge of Honour... I could go on forever but it's not exactly stuff that most people can identify with.
Some very good ambient stuff made with "real" instruments comes from Stars of the Lid (the tired sounds of stars of the lid is ace) and Jessica Bailiff (all 3 of her albums are good, but the newer untitled one leans on more traditional song structures - she's got a beautiful voice). Both do droning ambient music that swirls around and sends you into a trance. Very, very nice
Tip of the iceberg, me old china.