What are some good free electrical and computer engineering CAD packages?

I need to find some free electrical and computer engineering design packages that are actually effective. These packages need to cover power systems, embedded systems, and software engineering. Any suggestions?|||http://www.lerc.nasa.gov/WWW/K-12/freeso鈥?/a>|||I recommend TurboCAD even though the price is $100. It can basically do everything AutoCAD can do for a lot lower price.