FreeHDL: Project to develop a GPL VHDL simulator for Linux.
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]
Leonardo Spectrum: A synthesys tool, which will optimize your ASIC/FPGA/CPLD design. Evaluation license is available.
