It will probably be possible to construct something reasonably supercomputer-like with the Papilio platform soon. Altera has announced they're putting hard-wired floating point units on FPGA's and the top-of-the-line chip will be capable of an aggregate 10 teraflops. A board with one of those 1000+ pin BGA's would probably be pretty pricey, but something more reasonable could probably be made. So you would be programming a ZPUino with a large vector math unit bolted onto it or a bunch of them with smaller vector processors. Nice for 3D graphics or computer vision.