Automatic Python API documentation generation tools:
PythonDoc - uses StructuredText input format (not reST), and can produce HTML and XML output. It uses XML as an intermediate representation, to simplify the addition of new output formats. http://starship.python.net/crew/danilo/pythondoc/
Another PythonDoc - uses JavaDoc-style comments, and produces HTML and XML output. Can also be used as a library, producing ElementTree descriptions of your source code. http://effbot.org/zone/pythondoc.htm
Doxygen < http://www.doxygen.org > can create documentation in various formats (HTML, LaTeX, PDF, ...) and you can include formulas in your documentation (great for technical/mathematical software). Together with Graphviz < http://www.research.att.com/sw/tools/graphviz/ > it can create diagrams of your code (inhertance diagram, call graph, ...). Another benefit is that it handles not only Python, but also several other programming languages like C, C++, Java, etc.
Endo, part of the Enthought Tool Suite (http://code.enthought.com/ets/), is aware of Traits-based attributes (Traits is also part of ETS); uses ReStructuredText or plain text in docstrings and in plain comments that immediately precede variable assignments; and generates HTML output.
Other projects that can be used to produce API documentation: