Electric: Electrical CAD system

Electric is a sophisticated electrical CAD system that can handle many forms of circuit design, including:

• Custom IC layout (ASICs)
• Schematic drawing
• Hardware description language specifications 

It is a free and open software and works in windows, mac or linux operating systems! It can be downloaded from here. 

If you need to see the manual of the program, please go here. If you need more help, please go here.