Background
Sharp on electric energy $aving questions.
Gives good diagrams of switches.
Very good account of shocks by an engineer-type.
Thorough treatment of the relation of electricity to fires.
Big page with lots about other countries‘ electrical systems.
For the curious, this is how a GFI works.
Wikipedia's articles on GFI, Switch, Wiring, Shared neutral, Short circuit, Circuit diagram, and Receptacle testers.
Troubleshooting
Excellent on troubleshooting fluorescent lamps/fixtures.
Good on Christmas light problems.
These deal with X-10 systems, which I don't know that much about.
Here's a contractor giving basic tips so you don't look like a fool for calling him.
I found this Family handyman article to be fairly good on dead outlets.
Sam has a lot of info, some being about GFIs and home appliances.
Check this if you are looking for troubleshooting training software for use in industry.
Somewhat similar to my site in the troubleshooting problems it addresses; not as thorough, but a decent place to go if you’ve tired of mine.
Tools
Valuable Diagnostic Tool: This circuit breaker identifier leaves little need for guessing. I bought one and compared it with an expensive tool I have (that can do other things in addition) on seven circuits in my home. This "Circuit Detective" (not to be confused with me) did as well as mine. For the purpose of circuit identification, it is even handier than mine, so I am now carrying it to jobs in my main tool bag.
Another retailer shows many useful testers available.
How To
Has good photos of how to install a breaker in a panel.
Shows how to make some repairs and replacements.
Other
Special help for mobile homes.
Considerations when remodeling wiring.