How much do I love Wikipedia? It's the World Book of popular history; the dictionary of terms and ideas never touched on in Webster's; it's the future of information in the Information Age. I know there are errors and deliberate vandalizing upon occasion within it, but those who love the subject at hand watch over their chosen entries, and update and improve upon the material.
I was reading a particularly verbose recap of the latest Doctor Who episode on televisionwithoutpity.com (one of my favorite sites for many a year) and it was littered with references to arcane concepts and historical figures... which I could then look up on Wikipedia! I'd never heard of Steampunk, for example - an entire genre of historical/scifi/alternate universe fiction - and it's absolutely fascinating!