Google is theoretically the place to go, but it still isn't 100% efficient at finding relevant sites, much less expert sites.
Wikipedia is a good stop-gap for making Google-searches more efficient. It's not quite expert, but it's at least good in an "Ask A librarian" kind of way. And the Talk discussions on each page are quite interesting and show there are people who are passionate about even small details. One of the main downsides is there tends to be redundant pages, and a bit of anarchy to it because its almost a pure democracy (even maybe a syndicalist anarchy). Only the rational, 'guild' structure to it saves it, IMHO.
General interest topics (history, geography, etc..) are the best written on it, IMHO.
Apparently it doesn't score too much different than an average print encyclopedia.
Can't beat true expert opinions from academic, peer-reviewed references though.