RefDB is a reference database and bibliography tool for SGML, XML, and LaTeX documents. Command-line tools allow interactive or scriptable access to the data which are stored in a SQL database. RefDB can also be accessed through a Web interface, a SRU interface, or via editor extensions (Emacs/vim). Libraries for Perl and PHP are available for programmers. RefDB provides sophisticated character encoding handling, using Unicode by default.
SDoP (Simple DocBook Processor) reads a DocBook XML file, processes it into typeset pages, and outputs the result as PostScript (which can easily be converted to a PDF). It is "simple" because it supports only a subset of DocBook, and also because it does not make use of a DTD or stylesheets or any other heavyweight apparatus. It is a single program. SDoP is used to format the Exim reference manual.
MkDoc is a C and C++ code documentation tool. It parse complex code and still produces clear documentation for developers and library users. Unlike most code generation tools, it does not simply write generated code documentation with pieces of user text inside. Instead it handles plain documentation files with sections and other constructs (like Texinfo or LaTeX) and inserts pieces of generated code documentation on request. Thus it does not enforce any way of structuring your document. It has been designed to parse advanced C++ constructs including class inheritance, template specialization, and template instantiation. XHTML, Texinfo, LaTeX, and DocBook output formats are supported.