DocBook is an XML vocabulary which enables you to create document content in a presentation-neutral form that captures the logical structure of the content. Using the DocBook Project XSL stylesheets, you can publish DocBook content as HTML pages and PDF files and other formats, including man pages, HTML Help, and JavaHelp.
The wiki has become the clear choice for use among projects for their help documentation. Wiki Web Help takes the wiki concept and tailors it for use specifically with help documentation. It combines the best of both worlds, with operation similar to a chm viewer and the Web technologies that enable community involvement. It features a dual split pane with tabs for searching, index browsing, and display of contents (in a tree). Users can create and modify topics and pages. Pages can be tagged for index creation. Searching with highlighting is included.
Epydoc is a tool for generating API documentation for Python modules, based on their inline documentation strings (docstrings). It produces HTML output (similar to the output produced by Javadoc) and LaTeX output. It supports four markup languages for documentation strings: Epytext, Javadoc, ReStructuredText, and plain text.
TEKlib is a library and operating system effort. It runs hosted on platforms such as Unix and Windows. It can serve as a freestanding operating system on architectures such as the Playstation 2. It is also a middleware that provides a constistent interface across all hosting environments. Its freestanding nature, small footprint, and absence of global data recommend it as a layer for portability and code reuse in heterogeneous environments.
Synoptic is "GMail for your notes", meant to keep and categorize a large number of smallish notes and tidbits of information. Tagged overviews that retain order make it easy to maintain a good overview of your things. Adaptive tag clouds plus integration with browser bookmarks and forward/back navigation allow for easy navigation. Written in pure Python, it runs as a local Web server.
Ccdoc is a Javadoc-inspired tool that automatically generates HTML Web documentation from C++ programs by parsing the source file headers. It was designed to aid the collaboration between package users and package developers. It runs on FreeBSD, Linux, Mac OS X, Solaris, and Windows (98, 2k, Me, and XP).