The Electrical Wiring FAQ is everything you wanted to know about American (and Canadian) domestic wiring, and then some. Sadly, there appears to be no direct European or rest of world equivalents.
This FAQ is a monster, and so is split into two parts, the original text versions of which are (and these are FTP links) here (part 1) and here (part 2). There is also a HTML version available, but the old text version is the daddy, and so is likely to be more recent.
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