oh I just got kinda sad
they are so spectacular though.

bonobo, boards of canada, & cinematic orchestra are 3 of my favorites in this genre

also, for some more upbeat electronica with awesome spacey vocals, check out my friends electrodactyl

Thanks everyone, sincerely. I'm going to be up all night listening to this stuff now. One last request - recommend some mellow instrumental trip hop... something with no (or very light) vocals/samples. Chill-out trip hop, you might say. Maybe something sort of like the Urchin link I originally posted in this thread (second link). Anyone?

You might want to try Nightmares on Wax, DJ Krush or even old DJ Shadow and the Headz compilations released on the Mowax label.

Sundays on friskyradio.com is chill day. You can tune into great mixes by Lost In Sound, Vogelman and others.

To back track good mixes or albums not yet mentioned:
Banco de gaia: Last Train to Lhasa and Maya
William Orbit: Strange Cargo

I like early Kitaro.

One of my favorite downtempo mixes was done about 10 years back. Sort of an ethno-ambient-scifi mix. By me.
http://www.saintofspinners.com/music/Touched.mp3
No longer have the track list.

And for the trip hop...
Massive Attack - Mezzanine and Protection
not quite chill but pretty mellow.

I don't really know anything about trip hop, but it strikes me that the whole Witch House thing is kinda like a spooky version. There is some real crap, but some really nice tracks as well.
o0o00 has some nice stuff:
http://soundcloud.com/ooooosounds

White Ring also has some good stuff:
http://www.youtube.com/watch?v=_sGSntTw_Q4
I really like this one:
http://www.youtube.com/watch?v=TsFGEHZ8zyc&feature=related