giewiki is an adaptation of TiddlyWiki for the Google App Engine. As such it is probably the most feature-complete solution. While it is primarily intended for hosting on App Engine, it also works quite well for personal usage hosted by the App Engine SDK dev server.
It benefits greatly from the dual foundation of TiddlyWiki (adaptable design) and App Engine (simple, free hosting), but it does add most of the features you would expect to find in a multi-user wiki.