While I've linked to it several times, I've never spoken directly about Wikipedia, which is one of the most important sites on the net (and with the greatest potential). It also could use your help.
If you're not familiar with Wiki it is at its most basic a system for creating user-controlled collaborative webpages. In some ways it is similar to a discussion board, wherein anyone who visits can post a topic and then other people can reply. However, wiki uses this same idea for actual content, where the pages that are viewed on the website are created and continuously updated by the users. It is really an extension of some of the best parts of the web (democracy of ideas, real-time information, ease of use and access, flexibility) taken to its logical extreme into a free-for-all of information.
I first became aware of the concept through work, where a cow-orker and friend created a wiki site for our Engineering group. Really, an intranet wiki is where this environment really shines, as you are dealing completely with trusted users who are collaborating toward the same goal. So while usage isn't 100% and I'm still trying to get some people on board, most of what you could want at work (this document, that study, these specifications, those schedules, and etc.) can be found on our wiki site, and new stuff can be added by anyone at any time, with full text description. This is a far more elegant and intelligent solution than one gigantic "share" drive where the information owners often have cryptic and bizaare folder organization and its hard to tell what is useful and what isn't.
However, the Wikipedia is a far more ambitious effort using the wiki model. I'm hoping by this point you got an idea of what it is, but if not I'll explain anyway. It is a massive, collaborative, user-created storehouse for human knowledge.
Already, I find it to have some of the best information on the web. It's rarely been stumped when I was looking for something, and is starting to become my first stop when I'm looking for information. Understandably due to its current contributors, it tends to have computer-age scientific bent to it, but it gets broader every day. And while it was started by a few people, it is essentially self-organizing at this point, as there are more people trying to make it better and improve it than there are people posting articles that say "skjlsfj" or "Mark Johnson drinks pee".
In any case, despite this level of anarcho-synidcalist (or perhaps libertarian socialist) policing, there is still cost involved for bandwidth and server space and everything else that goes with hosting a storehouse of human knowledge. So my suggestions are:
1) Go to wikipedia.com and check it out. Try it out right now, and the next time you're curious about something, go there and see if there is an article, and see what you think of it.
2) If you're an expert or have some degree of arcane knowledge about something (anime, science fiction writing, fish, carpentry) consider creating or adding to existing entries.
3) Think about donating to keep the project alive.
Notes:
They also have a "random page" link (Try it!), which brought up the following five in order.
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