Linuxdoc-SGML is a text-formatting package based on SGML (Standard Generalized Markup Language), which allows you to produce LaTeX, HTML, GNU info, LyX, RTF, and plain ASCII (via groff) from a single source; due to the flexible nature of SGML many other target formats are possible.
This system is tailored for writing technical software documentation, an example of which are the Linux HOWTO documents. However, there is nothing Linux-specific about this package; it can be used for many other types of documentation on many other systems. The name is simply derived from its use for the Linux HOWTO documents. It should be useful for all kinds of printed and online documentation.
See Linuxdoc-SGML, and The current version can be found on sunsite at http://sunsite.unc.edu/pub/Linux/utils/text/, on tsx-11 on ftp://tsx-11.mit.edu/pub/linux/docs/, and on all mirrors (recommended). The latest patches can be found at ftp://ftp.cc.gatech.edu/pub/people/gregh/linuxdoc-sgml/.