It is designed to support digital designs written in VHDL or Verilog.
SynaptiCAD helps engineers think critically about their designs.
It is a design and verification tool that can be used by system designers.
HDL Works BV
Scriptum is a free text editor focused on VHDL and Verilog design.
Karnaugh Studio is a product line for students of engineering and professionals.
This free utility generates HDL Sine Look Up Table Modules in Verilog.