A GPGPU is a graphical processing unit, but with adaptations to make it possible to use it for general purpose computing as well. For those of you who followed Intel’s Larrabee project – that is a GPGPU. Intel’s project was stopped before it reached the market. Not an open source project, the Nyuzi Processor, implements a similar architecture.
The project is quite impressive. It features a pipeline vector FPU, multiprocess support, an L1/L2 cache hierarchy. It also comes with a LLVM-based C++ toolchain, software libraries and test benches and can be synthesized.
Check out the github page for instructions, the full Verilog source and all the associated tooling.