GHDL GHDL: A VHDL simulator and implements nearly all VHDL87 and some features of VHDL93. GHDL is written in Ada95 and it is a GCC front-end. [Open source, GPL] (Tools) http://ghdl.free.fr/
Leonardo Spectrum Leonardo Spectrum: A synthesys tool, which will optimize your ASIC/FPGA/CPLD design. Evaluation license is available. (Tools) http://www.exemplar.com/leonardospectrum/
VHDL Simili VHDL Simili: A fast VHDL Compiler/Simulator [Freeware]. (Tools) http://www.symphonyeda.com/products.htm
FreeHDL FreeHDL: Project to develop a GPL VHDL simulator for Linux. (Tools) http://www.freehdl.seul.org/