Originally Posted by suit2please
There is also OPR, Official Poker Rankings which gives you more information and is completely free. http://www.officialpokerrankings.com/
But like was already said both of them only collect statistics on SnGs and tournaments, not cash games.
www.pokertableratings.com (http://www.pokertableratings.com) tracks cash games, but only at 0.50/1$ and above.
And like D´wilius said your not alowed to have OPR,SS or PTR open while the poker client is running, but its perfectly fine to use them for post play analysis .