Other Places to Go
Oscar Voss' "unofficial, non-commercial Internet guide to Hawaii's highways, for 'roads scholars' and road users." I had immersed myself in this site for hours on end, and it was the prime inspiration for Full of useful facts, fun trivia, and interesting photos... highly recommended.
Scott Oglesby is a roadgeek in California obsessed with Connecticut. But his site features some of the best information on highway configurations, interchanges, and numbering that you'll find on the web.
Hawaii State Department of Transportation
The DOT website (and its Highways Division section) is fairly basic, but offers lane closure notices, laws and standards, and state route lists for all islands.
Honolulu Traffic Cameras
Easily one of the top web destinations in the state, this surprisingly addictive site allows live access to the City & County of Honolulu's network of traffic cameras. See also the live index of traffic incidents reported by the Honolulu Police Department.