How do I get this effect in Vegas 5 without the tedious placing together of ultra-short shots and/or repeated "flashes"? I know a little about the still image sequencing feature, which comes close.
you can also make a bright/contrast fx & then adjust the keyframes. After you do two keyframes (bright & dark) then you can copy/paste them. Then copy & paste those... etc.
then save that as a preset for later use. :) (remember, a strobe just isn't on/off, it's off & then brighter then a normal light)