You seen this? The new Google Website Optimizer.

Website Optimizer allows you to create multiple versions of your webpage (maybe one version with a red button and one with a blue) and evaluate which variation best meets your goals (whether that is sign-ups, purchases, or simply having visitors click to another page). The tool uses traffic data and advanced statistical formulas to figure out, according to your visitors, what makes your website the most useful.

You put some javascript in your code, they track you and voila!. The winner of their contest was this Candle Site. The thumbnail on the right is before optimization - and the second thumbnail is of the site after the Google Optimization team had a crack at it. They improved sales by 20% over a month adding another $20,000 to sales. Not bad huh?

The Google Blog always has some interesting stuff.