It sounds like you have tried several good ideas, but may have missed
some relevant suggestions from:
http://support.apple.com/kb/HT2090
If your iSight problem still occurs in more than one app
and more than one user account, the reset suggested there often restores proper function of inbuilt iSight.
However, if your built-in iSight still does not work after carefully following all the suggestions in the "How to Troubleshoot iSight" article, and if iSight does not show as a USB hardware device in your Mac's
System Profiler utility, yours is most likely a hardware problem. In that case, contact Apple or an Apple-Authorized Service Provider for service.
If you do not want to have it serviced by an AASP, the suggestion to use an alternative camera is a good one. For some info on the alternatives see:
http://www.mac-compatible-web-cam.com/
or this User Tip:
http://discussions.apple.com/thread.jspa?threadID=2018211
Mac Pro Quad Core (Early 2009) 2.93Ghz w/Mac OS X (10.6.4) MacBook Pro (13 inch, Mid 2009) 2.26GHz (10.6.4)
LED Cinema Display G4 PowerBook 1.67GHz (10.4.11) iBookSE 366MHz (10.3.9) External iSight