I've had good luck sawing plexi on my table saw using a 200 tooth plywood blade. We've sawn 1/4" and 1/2" plexi with very minimal chipping. We do feed very slowly, and make sure the piece is well supported. I would be dubious about trying to do any good joints sawing with a jig saw--just isn't going to keep things square, straight, and precise. I saw "we" because it's my brother and I doing this work. Here are the two things I've worked on so far: Reservoir. Ignore the thingey on top, it's for this water block:
Heh, did anyone else notice that the only 'visited' links linear had in his 2 pics were both saying something about some 'hottie'?