adx is a minimalistic but massively Web-enabled address book that runs completely in your Web browser. It's OS-independent and supports comprehensive details for each contact entry, including user identifiers and profiles for Skype, Twitter, Flickr, Delicious, Facebook, LinkedIn, studiVZ, instant messengers, etc. It supports the hCard and XFN microformats.
xmlroff is a fast, multilingual, multi-platform XSL formatter that transforms XSL-FO documents (or any XML with an appropriate XSL stylesheet) into PDF or PostScript. It aims to excel at DocBook formatting, and it integrates easily with other programs and with scripting languages.
The docbookm package is contributed with LayManSys and contains very simple XSLT drivers for generating XHTML chunks from DocBook XML. This package does not require an installation; you only have to unzip the package's contents into a directory of your choice and start using it. There is no special documentation available. Use the file abstract.xsl for transforming an abstract and section.xsl for transforming sections. All other .xsl files are only includes needed by those two.
lxml is a Python binding for the libxml2 and libxslt XML processing libraries. It aims at ease of use of the API for Python programmers and exposing the many libxml2 features. It implements the Python ElementTree API on top of libxml2. It extends this with support for XPath, XSLT, Relax NG, XML schema, and more.