700/1759/950, is supposed to be pretty average.
738/1782/990, as a little higher stable clock.
740/1850/1060, as a higher clock that has known to work, but I heard pussing the memory clock over 1000 on the 8800GT can have bad side effects.
Its really not that hard, just push it up a little bit, run Furmark + GPU-z for five minutes, if you dont see any problems, push it up a little more. Rinse and repeart. There will get a point where the card starts to get hot or doesn't work correctly, once you hit that turn it down a little, and run Furmark for 30 minutes. If there are no problems your probably at your max OC.
Or just use ATI Tool as amir said.