The only variable-speed video camera I know of is the Sony Varicam, and those can be extremely pricey (not sure of rental cost exactly). There are dedicated high-speed video cameras out there too, but I think those are even more expensive and harder to come buy.

That leaves you with a couple options: shoot on film (also expensive), slow down your footage in post (this can actually look halfway decent as long as you use frame blending and don't slow it down more than 50%--you can get away with even more if you use After Effects 7, it apparently has some sort of motion detection-based speed adjustment that I have heard does a pretty good job), or find some stock footage on someplace like Artbeats (never used their service, so can't vouch for it).

I'm wishing all the time that I could shoot true slow-motion with my video camera, so if anyone can think of better solutions (or a lower-cost I'd love to hear them as well.

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Andrew Gingerich
Exploding Goldfish Films
Check out my vodcast on iTunes: http://phobos.apple.com/WebObjects/MZStore.woa/wa/viewPodcast?id=96931870

For slow motion, I never playing with my camera
I always play in editing

Nada Taufik
Film Maker
pink_rebels?filmsindie.com
http://www.filmsindie.com/pinkrebels