Yep... I've been reading the source and some has good comment bocks and other parts... not so much.
http://libogc.devkitpro.org/ does document some headers, but is missing the following files:
asndlib.h, debug.h, gcmodplay.h, gcutil.h, iso9660.h, mad.h, mp3player.h, network.h, ogcsys.h...