I recently discovered this project (opensource) thanks to a post in SEPY feature requests. Natural Docs is an open-source, extensible, multi-language documentation generator.
It has native support for C#, Perl and ActionScript2 (PHP, Python, etc. has basic support).
It seems a really valid project, the problem (for me) actually is that is doesn’t support javadoc, even if I read on its forum that he’s planning to support it in the future.
Natural Docs requires Perl 5.05 or higher to run. If you’re using Linux or Mac OS X, you should already have it. If you’re using Windows and haven’t installed it yet, you can get ActiveState’s ActivePerl for free.
There are free versions available for many other platforms as well.
Download Version 1.34 from sourceforge.net site