It is without a doubt the most conspicuous example of user-generated content on the World Wide Web: Wikipedia (www.wikipedia.org), the free, open source, online, collaborative, multilingual, and controversial encyclopedia, written and edited by its users, misunderstood and mistrusted by many. Love it or hate it (there seems to be no middle ground), this ginormous, web-based reference source has had an impact that would be tough to overstate. Here's what you need to know to understand how Wikipedia works, and if you are so inclined, join the ever-expanding ranks of contributors to this unique publication.