I'm using a Canon 350d; it's got fully manual exposure settings and can capture repeatedly when the button is held down. I found shutter speeds in the range 1-2 seconds give a nice motion trail but allow a high enough frame rate for coherent motion from one frame to the next.
When comping the stills back into a movie, setting the speed at 2 frames per image with frame blending enabled worked very nicely. (i.e. on twos with mixes).
If I'm going to do any more more of this, I'd definitely like a remote shutter release switch. Ultimately a timelapse controller for this camera would be nice too!