Take a look at these two sites:
http://thottbot.com/?t=Enchanting
http://wow.allakhazam.com/dyn/skill333.html
I’ve found that both are lacking formulas here and there, so I usually end up using both. One nice thing about allakhazam’s listing is that you can quickly tell which formulas are dropped by mobs, as they are listed between < > symbols.
Best of luck.