For some time, I’ve used Crazy Egg to understand where people click on this blog, which uses a several techniques include a heatmap to report the results. However you only see what works post event.
Large companies use focus groups to test site layouts, during which they both monitor where people click and also eyeball movements. However, such tests are prohibitively costly for most firms. Hence, this is an intriguing site called “Feng GUI – Feng Shui for Graphical User Interfaces“.