TeXML is an XML vocabulary for TeX. The processor transforms the TeXML markup into the TeX markup, escaping special and out-of-encoding characters. The intended audience is developers who automatically generate [La]TeX or ConTeXt files.
ZML, the Zeitung Markup Language, is a simple CMS for small newspapers. It was specifically designed to publish a student newspaper in print and on the Web. It uses LaTeX and XHTML. So far, it is documented in German only.
texd runs TeX as a daemon, and provides a callable function interface. This allows TeX to be used as the typesetting engine for interactive applications.