The Enhanced Ocaml Documentation is provided by Hendrik Tews; basically it visually highlights any difference between the previous and current version of the documentation. Here is how he does it:
I diff the txt versions of the reference manual and change the html version by hand. For the grammar rule index I use a tool and manual editing.
–Hendrik Tews
Wow. What a labor of love. Be sure to give him a hand!
(via Caml-list)