These are some items of interest that we've developed or are working on.
I have published descriptions of some XML applications available, including this Web site, an invoicing system, and an ISO 8601 date/time XSLT processing library.
When I'm learning a formal language, I find it helpful to create my own hyperlinked reference documents. Even if I never look at them again, the process of doing so helps me learn them more fully. (Plus, I often find errors in the specifications that way.) I created such a reference for SGML, the International Standard on which XML is based, and a partial one for HyTime, the International Standard for hyperlinking, hypertext, and multimedia.
DSSSL is the International Standard for stylesheets. With a few minor tweaks, it's also a fairly powerful SGML transformation langauge. Many of the lessons learned from DSSSL were applied to the design of XSL, especially in the separation of XSLT as its own language.
At the request of the W3C XML Working Group, Chris developed a stylesheet for HTML tables; this was included in the stylesheet used to format the XML specification's Word and PDF versions.
We're also working on prettier versions of things here, but in the meantime, here's a big bucket of things in various states. Links in these files aren't guaranteed to work at all.