Markup Languages

Electronic Documents Markup - A brief explanation of what markup languages are and where they come from.
web.cs.wpi.edu/~kal/elecdoc/EDmarkup.html

Microformats - Simple data formats built upon existing and widely adopted standards. Overview, specifications, events, and discussion.
microformats.org/

Project Xanadu - The original hypertext project. Includes a history of the project and gives credit to the early developers of markup languages.
www.xanadu.com/

whatis.com: markup - A short definition.
whatis.techtarget.com/definition/0,289893,sid9_gci212527,00.html

YAML Ain't Markup Language (YAML) - A straightforward machine parsable data serialization format designed for human readability and interaction with scripting languages such as Perl and Python.
yaml.org/