blackc2004

This plugin will let you track which pages your logged in users are viewing. It logs username, ip, datetime, refere and url viewed. This newest version adds a basic graphical represnation of the users and what they have viewed. You can also filter by user.

UserTracker

This plugin will let you track which pages your users who are logged in are viewing. It logs the username, ip, datetime, referer and url viewed.

dubhunter

There are quite a few free, or near free tracking solutions out there, but many of them require a JavaScript snippet to be placed on your page. 
This is where DBD Footprints steps in. A new menu item will be added to the Options menu of WP. On this page you will be able to edit the code/text 
needed for tracking or anything else you can dream up.

DBD Footprints

Add code or other text to the footer of the blog. Works great for Google Analytics, Extreme Tracking, and many others.

UserTracker vs DBD Footprints