Years ago I tried to find a clear and useful reference on 'comparative advantage', a foundational theory in economics. I was frustrated by a great deal of noise, and at that time the Encyclopedia Britannica didn't help.
Today I tried again, and Wikipedia had a good summary. I knew Wikipedia was good, but it's becoming astounding.
Update 9/25: See the comments. Brittanica actually has a reasonable article. Hard to believe that's new, so either I misremembered using them or I bobbled my old search. So I'll still say Wikipedia is amazing, but I should have been nicer to EB.