HTML Helper Mode
- Major mode for editing HTML files. The current address of the mode originally written by Nelson Minar and now maintained by Gian Uberto Lauri.
- http://www.nongnu.org/baol-hth/

Sxml-Mode
- A mode for XML in (X)Emacs using the Simple API for XML (SAX).
- http://koala.ilog.fr/plh/sxml.html

XSLT-Process
- A mode which allows running an XSLT processor on a buffer.
- http://xslt-process.sourceforge.net/

Html-Helper-Mode
- The original HTML mode by Nelson Minar.
- http://www.santafe.edu/~nelson/tools/

Emacs HTML 3.2 Mode
- An Emacs major mode for editing HTML files by Axel Beckert.
- http://fsinfo.cs.uni-sb.de/~abe/htmlmode/

PSGML Mode
- Major mode for editing SGML and XML documents.
- http://www.lysator.liu.se/projects/about_psgml.html