Just came across iVideo on freshmeat. I downloaded it to see what it does, and lo and behold: it captures DV video from my iSight camera!
I just captured a short (9 second) but huge (180MB) video clip, and it looks like it's a standard DV file (QT Player opened it - I didn't try importing it into iMovie, but that shouldn't be a problem).
With this and evoCam, there are a few options for iSight users to record and publish stuff from the camera.