I had discovered Wikipedia, the free encyclopedia a few years ago. It started on January 15, 2001 and today it is a humungous collection. The best part of it besides it being absolutely FREE (in the truest sense of the term), is that it is a collaborative effort, which means you can also become an active contributor to this innovative project.
It is hosted by the Wikimedia Foundation, which operates several other multilingual and free content projects, like Wiktionary, Wikibooks, Wikiquote, Wikisource, Wikispecies, Wikinews, Commons and Meta-Wiki.
Visit http://en.wikipedia.org/ for a Wikiexperience!