Fortran Wiki
Doxygen

Doxygen is an automatic documentation tool that is now compatible with Fortran. This tool supports pretty printing, call graph generation, man page generation, and LaTeX and HTML documentation files. Fortran support was first introduced as a patch, and has subsequently been integrated with Doxygen as of version 1.5.4. Some details and examples can be found at http://www.dougdevel.org/index.php?page=doxygen, but these may be somewhat outdated. The Doxygen homepage is at: http://www.stack.nl/~dimitri/doxygen/. Currently there is no documentation on the Doxygen page about documenting Fortran sources, but Fortran is listed as a supported language.

Homepage: http://www.stack.nl/~dimitri/doxygen/