This picture of a home-made vertical panel saw was posted on one of the WoodWeb forums. As its maker puts it, "it's not much to look at but it works very well."
I bet it does, and it probably cost very little to build. I like the way he connected the tool to a counterweight; presumably, the cable runs up and over a pulley and then down to a weight behind the tool.
I've used a similar counterweight setup for production work with a router – though it's scary now to think of what might have happened had I bumped into the spinning bit.