Actually, at least Marriland and Metalkid's Pokémon Page have actual downloadable IV and/or damage calculators, and as far as I know Metalkid's is as thorough as they come (although the latest one is just in beta and his progress on it is very, very slow).
That said, I don't know the formulas off the top of my head, but I know that Bulbapedia should have accurate ones. I know, I know, we're trying not to borrow from them or anyone else, but it's the same formula no matter where you get it from so you might as well. Smogon and some mechanics pages on the Cave of Dragonflies website should also have the correct formulas as well.