The xat wiki was created in 2007 as a way for users to share their knowledge. It received a good number of hits, but not many users actually contributed, and some even vandalized pages or made spam pages. Later it was closed, only to re-open in 2008 with only certain users given the ability to edit pages / add new ones. To other users, it's view-only.
Meet the writers, on the Wiki Editors list!
Also, xat wiki is available for many languages, they are: English, created in 2007; Spanish, translated in February, 2009; French, translated in February, 2009; Turkish, translated in November, 2009; Portuguese and Italian were translated at the same time, April, 2011.
You may submit articles by going to the Submitting page and following steps there.