Get an XLR8 InterView. It is a USB analog video-in with Strata VideoShop 4.5. It's much more powerful than iMovie, albeit not quite as easy to learn, but it costs only $90 if you shop around (---> CDW, $87).
I use one with my G3/350 and it works impeccably. Of course, it does not support DV, nor does it have a video out.
tooki