I presented to LA.pm on the subject of A/B testing. That is where you present people with two versions of the same thing, track them through your site, then decide which version gets more people doing the things you want.

For those who are interested, the slides are available at http://losangeles.pm.org/presentations/ab-testing/. There are also sample programs linked from the presentation for evaluating the results of an A/B test.

PS I developed and presented this on Firefox and it worked fine. But it doesn't work well on IE. I'm not sure why not.