What you can see here is a first live version of AtomicWiki, my XQuery-based Wiki engine. AtomicWiki started as an experiment to create a simple blog on top of eXist's existing Atom support. Eventually, more and more features were added during the past months, so the project has more evolved into a wiki-style system than "just" a weblog.
AtomicWiki is entirely based on the Atom Publishing Protocol and syndication format. All entries are stored as Atom feeds in eXist. We use the Atom Publishing Protocol to create and manipulate feeds and entries. Nearly all the functionality - except one Java function for parsing Wiki markup - is implemented in XQuery with the help of some XSLT and Javascript.
What makes AtomicWiki really powerful though, is its tight integration with XQuery!