I develop another extremely simple (but cool) extension to mediawiki, it works like the Graphviz extension, and it uses Batik from Apache as an SVG to png render. The extension is about sharing UML graphs or Images on a developers team. With this you can use Your favorite UML modeller (Together, Argo, Omondo, …) and export the format to SVG, them you can put on the wiki and at least another developer/analist can modify the XML on the wiki, and show results online.
You can view this plugin in action at my wiki
Yo can download and test it on the project information page of the wiki.
All comments and suggestions are welcome