Proteus PCB design - Proteus PCB design combines the schematic capture and ARES PCB layout programs to provide a...
simavr - a lean and mean Atmel AVR simulator for linux
EasyEDA - EasyEDA - Web-based EDA suite; runs in browser.
Xyce - Xyce is an open source, SPICE-compatible, high-performance analog circuit simulator, capable of solving extremely large circuit problems by supporting large-scale parallel computing platforms.
QUCS - Qucs, briefly for Quite Universal Circuit Simulator, is an integrated circuit simulator which means you are able to setup a circuit with a graphical user interface (GUI) and simulate the large-signal, small-signal and noise behaviour of the circuit.
SimulAVR - The SimulAVR program is a simulator for the Atmel AVR family of microcontrollers.