This free online encyclopedia has achieved what Wikipedia can only dream of - Quartz

"The Stanford Encyclopedia of Philosophy may be the most interesting website on the internet. Not because of the content—which includes fascinating entries on everything from ambiguity to zombies—but because of the site itself. 1 Its creators have solved one of the internet’s fundamental problems: How to provide authoritative, rigorously accurate knowledge, at no cost to readers. It’s something the encyclopedia, or SEP, has managed to do for two decades ..."