Formerly called "The HULK", Manticore is an open source hardware design for a 3D graphics accelerator. It is written entirely in VHDL.
http://icculus.org/manticore/
Aims to make VLIW and other novel ILP architectures hundred percent compatible with popular existing architectures such as PowerPC, x86, and S/390, as well as the Java Virtual Machine.
http://www.research.ibm.com/daisy/
Provides a collection of free, public-domain or shareware, VHDL documentation, models, and tools.
http://tech-www.informatik.uni-hamburg.de/vhdl/