Over the past week, I've developed a calculator for several Basketball Advanced Statistics. I did this after growing frustrated with having to calculate them by hand for preseason games. During the regular season, http://www.basketball-reference.com/ and http://www.hoopdata.com/ do a wonderful job of providing these statistics on a per-game and season basis.
Still, having this calculator means that as long as you have the raw data, you can calculate advanced statistics for whatever you want. Perhaps you want to know Brian Cook's eFG% when playing the Bobcats. Why you would want that information, nobody knows, and you probably need to seek medical attention, but the fact is that you can.
The Calculator is still a work in progress, as I still have several major statistics I need to add to it. It might take a while, but I'll get them up eventually.