LagMeter has just been introduced and helps you quantify your lag when playing online PC gaming. The great part is that it tells you whether you are causing the lag, your network, or the game server. Get it here. It is in beta right now but that shouldn't stop you.
"Harlan Beverly said the toughest challenge about developing LagMeter was to quantify Lag in a meaningful metric that made sense. “LagMeter solves this by introducing a new metric, Lags per Minute (LPM), which is essentially the number of measurable Lag events in a minutes worth of game-play.” For a formal definition of Lags Per Minute, click here. In addition to displaying Lags per Minute, LagMeter also measures and displays our tried and true favorite metrics – Ping and Frames Per Second (FPS). It even has an advanced configuration tab that allows the user to tailor exactly what is being measured based on which game they are playing or which network port or device is running the game. "