From the “this is so cool” department…
Wikipedia is a free encyclopedia that is being written collaboratively by the various readers. The site is a WikiWiki, meaning that anyone, you included, can edit any article right now by clicking on the edit this page link that appears in every Wikipedia article except for a few protected pages.
The project was started on January 15, 2001 and there are 190013 articles in English that are being worked on with many more articles being written in other languages. Every day hundreds of contributors from around the world make thousands of edits and create lots of new articles.