I use Crazy Egg, StatCounter and Google Analytics.
Crazy egg is an interesting website which provides a thermal heat web page which shows a lighter colour for exactly where your visitor clicks on your site.
Statcounter tells you everything you need to know from keywords, meta tags and html errors.
And Im sure you familiar with Google Analytics which puts data into graphs to make data much user freindly and easy understandable.
http://crazyegg.com/
http://www.statcounter.com/
http://www.google.com/analytics/
Have fun