I found my Intel Developer article The XML Menagerie. It discusses a variety of XML technologies, including WXS, RELAX NG and XLink/XPointer.
I also started on an Akara site for 4Suite, focusing on the RDF and respository features.
The Akara stuff is fun to put together, and I hope shaping out to be useful docs. I need to implement sophisticated ordering of some sort in the RDF query to organize the indices a bit more. I also have to add search (should be a snap) and some better style. I'm also contemplating the annotation features of crit as a possible addition. Thanks to vdv for pointing it out.