(1) If you want to make your own mod then:
http://cs.elderscrolls.com/constwiki....php/Main_Page
is a good place to start.
(2) Contains info on all skills:
http://en.wikipedia.org/wiki/The_Eld...ills#Athletics
(3) A fan based site:
http://bloodandshadows.com/
(4) Another site:
http://www.oblivionicus.org/
Thats all I know for now :P