Quite a while ago I wrote two articles on moneyless.org. One about free wiki software and the other about free wiki hosting. Of course I have a strong bias towards MediaWiki here.
Good news for freedom loving travelers. The Wikitravel community and its content has been freed. The website was bought by a company for more than million dollars a couple of years ago and this year the community revolted and moved everything to the Wikimedia Foundation - a 501(c)(3) non profit that is extremely unlikely to ever sell out.