Via del.icio.us - CrazyEgg, which hasn't yet launched, will be providing a service that allows websites to install software to track mouse movements, hovering & clicks. Below is a sample from their site:

While this isn't quite as useful as the eyetracking studies that monitor where users look, I think it will help to reduce problems in information scent and improve usability. I'm certainly planning to install it at SEOmoz as a trial once it launches.