I suggest you have a look at the Sphinx project: http://sphinx.pocoo.org/
With Sphinx, you mark up you documentation using reStructuredText. Sphinx converts the documentation to HTML, Latex (which can be used to create nice-looking pdf documentation) or MS HTML Help format.
Examples of Sphinx documentation:
Since Sphinx is written in Python, most of the projects currently using Sphinx are Python-related. Sphinx is however a general-purpose documentation platform, well-suited for most documentation tasks, I would imagine.
I have found Sphinx easy to use, and able to produce very nice-looking HTML documentation.
Some key points, from the Sphinx website:
- Output formats: HTML (including Windows HTML Help) and LaTeX, for printable PDF versions
- Extensive cross-references: semantic markup and automatic links for functions, classes, glossary terms and similar pieces of information
- Hierarchical structure: easy definition of a document tree, with automatic links to siblings, parents and children
- Automatic indices: general index as well as a module index
- Code handling: automatic highlighting using the Pygments highlighter
- Extensions: automatic testing of code snippets, inclusion of docstrings from Python modules, and more