How do you do your usability testing?
yeti: Find 3-5 people/friends, get them in front of a machine and run through it.  No fancy software, just sit next to them and observe, ask questions if they seem stuck or confused.  We do it every couple of weeks, seems to work well.  Also consider paying for 1-2 hours of a usability experts time to review your site in person, a very good investment.