Open source EDA tool link / resources ?

Magic, the VLSI layout editor, extraction, and DRC tool  link

XCircuit, the circuit drawing and schematic capture tool link

IRSIM, the switch-level digital circuit simulator link

Netgen, the circuit netlist comparison (LVS) and netlist conversion tool link

Qrouter, the over-the-cell (sea-of-gates) detail router link 

Qflow, a complete digital synthesis design flow using open-source software and open-source standard cell libraries link

PCB, the printed circuit board layout editor link

verilog , you can execute verilog code , link 

verilog :Easy-to-use graphic user interface provides productive environment for novices and experts—Silos selected by seven popular Verilog textbooks and used in the majority of university VLSI design courses ink 

PCB Simulator : pcb simulator, can be downloaded here   

Model Simulator student version : it is vhdl /verilog simulator , download