The Wiki Way
Wiki is a fairly new concept to the web, so this will take some getting used to.
Wiki websites are editable in the same place you view them -- in your browser. Every page will have a link to "edit this page". TextFormattingRules are much simpler than most other markup languages. Basic text formatting such as headlines and lists should be very intuative.
Where do I try it?
Start with the SandBox. Write something in there to see how it works. Then find a place on the site you can add to and have fun!
What about security?
There is none. Nothing is to stop you you from defacing a wiki website except that fact that it is so easy there is little glory in doing so. My hourly backups and complete page revision history say that I can easily recover anything lost, but nothing is stopping you from editing any page on this site.
There aren't many. Mostly just respect what has been written. You can refactor discussion, but don't put words in peoples mouth. See the RealNames page.
For further reading, check out http://c2.com/cgi/wiki?WikiSocialNorms