...I think Kraftwerk more than any other act practically defined futurism in music for all future acts with their music that conjured images of robots, machines, computers, programming and a stiff, mechanical vibe (note that I still think Kraftwerk sounded somewhat ''warm''; probably because of their analog syntheseizers)... At this stage, it's really more ''retro''-futuristic than anything but whatever

Some others that come to mind:

Sun Ra (duh!). The sheer strangeness and "otherworldly" vibe of the tonal language on records like "Cosmic tones for mental therapy", "Heliocentric worlds 1 and 2" and "Magic city" combined with how early he was with using the studio as an instrument (delay, reverb, echo etc.) and on some recordings even primitive keyboards make him sound very futuristic, not just in the context of the time but even by modern day standards to me.

Jimi Hendrix. Especially when he made songs like "voodoo chile" or freaked out with the guitar-effects. There's something very cool to me in the way he combined elements from ancient delta-blues (lyrical cliches, riffs etc.) with "space-elements" (lyrics that reference the sulfur mines of jupiter and (then) state-of-the-art guitar effects). Some would say that the blues-elements make him less futuristic but I'd argue it's the opposite because blues/blues-rock has not exactly been very open to "spacey" stuff historically but has instead thrived on "authenticity" so that he was working partially within the confines of those genres make him come across as extra futuristic.

P-funk (duh). I don't know how you can hear a song like "Flashlight" and NOT feel that these guys fit the (static) definition of futuristic. Just like with Hendrix, they were also not afraid to take off to space which of course is quite futuristic since spaceships and going to other planets and stuff was-and remains-something associated with the future.

Devo. Futuristic is often associated with something that sound "stiff" and mechanic, a bit robotic. While this band worked within a conventional rock-band form, their stiff, jerky and jagged rhythms to me just give off this vibe of rock/pop/new wave as played by robots. Obviously, Gary Numan and others had that too but Devo pioneered it. The funny thing is that Devo's approach was almost completely lifted from Captain Beefheart's late 60's-early 70's music but whereas Beefheart's music constantly changed the riffs and rhythms (not very futuristic since it gives off a non-programmed, organic vibe), Devo essentially took Beefhearts riff/rhythm-combos and "looped" them and bang!-they arrived at something fresh by stripping things down...

Chrome in 78-80 or so. Pretty much the same as Hendrix; Chrome worked with forms of music that aren't really associated with a futuristic vibe (in their case:garage-rock, proto-punk, retro-psychedelia etc.) but then applied tape-manipulations, vocoders, synths, ''industrial'' sound-effects and other studio-tricknology to the whole shit as well as having wonderfully (retro) futuristic cover-art and lyrics.

Judas Priest on "Stained Class" (1978). I just feel that the combination of the guitar-sound and the bands stiff, sharp and jagged way of playing (not to mention the cover-art and lyrics) essentially divorced their music from "classic rock" and the loose, jammy, blues-based, more rootsy styles of their heavy predecessors like Zeppelin, Sabbath or Deep Purple.

Africa Bambataa. Most early Hip-hop hits were disco-derived so obviously, dude and the Soulsonic force kind of helped introduce the more "futuristic" vibe to Hip-Hop when songs like "Planet Rock" hit...

Kool Keith. Another obvious Hip-Hop example even if it was more the lyrics than the music in his case. Still, I guess the Dr. Octagon album (not to mention Black Elvis) aimed for that "futuristic" vibe and succeded I guess even if I don't think the beats were too hot and only a few really felt futuristic.

voivod in their prime (=late 80's). My metal-pick from that era; everything from the music with lots of sharp and jagged flat-5th power-chords to the album-covers (GREAT!) to the lyrics give that vibe. Watchtower's "Energetic disassembly" is another, earlier example of a metal-album that I guess qualify for that vibe. Oh yeah, first Cynic as well: http://www.youtube.com/watch?v=5_09IAg12q8
I always thought this record sounded like a joke with the synth-basses and vocoders and smooth jazz-influences but it's supposedly a classic.

STRONGLY agree with Art of Noise as well; that was the 80's overblown machine-park in full effect