blockdiag and its family generate diagram images from simply text file:
Features:
Generates beautiful diagram images from simple text format (similar to graphviz’s DOT format)
Layouts diagram elements automatically
Embeds to many documentations; Sphinx, Trac, Redmine and some wikis
Enjoy documentation with blockdiag !
Google Groups: http://groups.google.com/group/blockdiag-discuss/topics
Twitter: #blockdiag
Interactive Shell: http://interactive.blockdiag.com/
Issue Tracker: https://bitbucket.org/tk0miya/blockdiag/issues?status=new&status=open