Receptional - 10:04 am on Apr 2, 2010 (gmt 0)
Three really useful tools when it comes to usability are google website optimizer (or is it Google conversion optimizer? There are so many tools now), which does a:b testing of on page content and "Crazyegg" which maps the mouse movements of users over the page. The third tool would be ClickTracks, which looks at where users click on a page in a visually intuitive way.
I would investigate these.