Doxygen
From GnuCash
Doxygen is the central point for source documentation at this moment (January 2011).
It is a software which extracts (special) comments from sourcecode to produce source documentation. It can be run on your local copy of the sources by
./configure --enable-doxygen --enable-html-docs make doc
This is done and put online on a regular basis at http://svn.gnucash.org/docs/HEAD/.
Links
- GnuCash Doxygen Source Documentation http://svn.gnucash.org/docs/HEAD/
- Doxygen Documentation http://www.stack.nl/~dimitri/doxygen/index.html