I've just registered at hittail.comThe purpose of this service is to collect and present stats on what long tail search terms people have used to find your web pages. The basic service is free.This tool seems very good for sites with 100 pages plus. The basic theory seems to be:1. Register and install the javascript code on your pages. Takes about 2 minutes.2. Start collecting stats3. Look for patterns in the stats4. Create new pages, or optimize existing pages for those long tail search terms with high frequency5. Dominate the niche

Your internal search data is also a great place to check out. Put it into AdWords traffic estimator, find high traffic keywords with low competition, and you win!