Perhaps the hardest part of being a Webmaster is coping with success. When a Web site is small and not visited often it is easy to browse the server logs and see who is accessing the site and what pages they are visiting. When you get on someone's What's Cool page your whole world changes. Reading through a log file containing 100,000 hits a day and making sense out of all that data is next to impossible.

These are the newest website visitor tracking systems that there are. Some are free, but others are not, you’ll have to check them all out, and see who has the best metrics for you.
First, bookmark this page; You’ll want to come back here to complete your research.

Threads
A thread tracks a visitor to your site from the first page visited to the last. Each thread consists of one or more pages that a user looked at during the visit. Looking at the threads gives a good idea of how people navigate around your site. You can also get an idea of how many pages people are looking at and how long they stay at your site.