Is there one?
Good question Benjamin, I'm glad you asked! I guess you found http://docs.moodle.org/dev/Developer_documentation though it's not really a TOC. Once Moodle 2.3 is out we'll hopefully have time to make a TOC. I've created an issue for it - MDLSITE-1768 - so we don't forget!
Cheers Tim, the Special:Categories looks like it will do the job