CMOSexod.com - For advanced hobbyists: share free microprocessor and DSP IP cores written in Verilog or VHDL.
E-Risc - Project to design and implement scalable RISC microprocessor for embedded applications. All architecture and source code to be released under GNU General Public License, or a slightly modified version that includes hardware, not only software.
The Freedom CPU - F-CPU, mainly dedicated to pure SIMD superpipelined 64-bit RISC CPU, and the sources. Open Source, GPL.
STM - 32-bit, 2-way superscalar RISC processor, designed in a HDL. Source downloads. This one is actually working.
Sun Community Source Licensing (SCSL): picoJava - A core is the central component of a processor or controller chip. Chips using picoJava core are well suited for consumer electronic products running Java programs. Sun Microsytems.
Open Source Soft Microprocessors - Free licensing of soft microprocessors lets designers easily modify FPGAs and gives greater visibility into architectures; explains implications of associated licensing models. Dr. Dobb's. (March 7, 2007)