] Wikipedia is a multilingual project to create a complete
] and accurate open content encyclopedia. We started on
] January 15, 2001 and are already working on 110789
] articles in the English version. Visit the help page and
] experiment in the sandbox to learn how you can edit any
] article right now.

Amazing and extensively-hyperlinked informational resource available in a dozen languages.

I ran across a few of its pages while searching for information on Iraq's history, and found not only that, but also what's effectively "current events" information, current as of a few hours ago.

One of the things that I *really* like about Wiki -- if you see an error or omission on a page, you can go in and change it yourself! Just click on the "Edit this page" link at the bottom of any article. Or click on "Recent Changes" to see when other changes were made, who made them (by name or IP), or what previous versions of articles said.

The pages are a bit slow to load at times, but the quantity of information makes it worth it.

An encyclopedia that is created and alterable by everyone.

An encyclopedia that is created and alterable by everyone. I've found myself using this more and more recently.

An encyclopedia that is created and alterable by everyone, licensed under the GNU FDL.

Wiki to the extreme.. In the licensing area, they even keep the threat letter templates they use and keep track of all the places and articles they know of that use the content without the required attribution.