Parallella: 18 CPUs at 800MHz, 25 GFLOPS, 1GB DRAM, $100.
This credit card sized platform combines FPGA, ARM, and DSPs.
project needs more backers on #Kickstarter
in the next 2 days
Edit (27 Oct 2012): The project reached its funding threshold on Kickstarter. Last chance to grab one of these nice boards (expected May 2013) before it closes soon today :)