Hi, i just stumbled across a website that lets you build circuits and simulate them in your web-browser, its called "CircuitLab", thought it looked useful for virtual testing:
https://www.circuitlab.com/
Where i found it:
http://www.keelynet.com/news/022812a.html
https://www.circuitlab.com/
Where i found it:
http://www.keelynet.com/news/022812a.html