I took high speed images like that with a trigger I built from plans in Popular Electronics in the early '90's. I still have my rig, which worked beautiflly. I did get some decent shots but it was a pain to have to shoot a roll of film and get it developed each time to tweak my trial and error. Of course the lack of thyristorized flash on my rig didn't help with the tweaking. I was heavily into Photography back then, but I've only bought my first DSLR last month (Nikon D90), because the quality of digital never seemed good enough. I was trapped between my film Nikon SLR's and digital point and shoots. I'm very impressed by the D90.
I have a bit of buyer's remorse over the 18-200 zoom though. My 18-year-old 35-70 AF lens is a tiny bit sharper. The new lens has some significant barrel distortion and is so big that it casts a shadow when I use the pop-up flash and a wider zoom. It's not bad, but given the trade-offs, I don't think the added zoom range was worth the $800 when I already had older Nikon AF lenses. On the other hand, when I'm out shooting, the zoom range is just stunning and I'm planning to try out some distortion correction software.
Also, no suggestions for where to get some cheap phototransistors? I have a couple of empty single-use flash cameras to use as "practice" building slaves. I toyed with the idea of connecting 8 to an Arduino and trigging them in sequence within the time of a single exposure, but the SB-800 has a repeating mode that's fast enough.