I've just uploaded a big update to the Feed Statistics plugin for WordPress. This new version allows you to track which posts your subscribers are reading and which links they're clicking on. It also has better feed reader statistics, and a more organized administration menu.
See the updated homepage for a full writeup of the new features.
To install this plugin, download the zip file of the latest version here, and overwrite feed-statistics.php in your blog's wp-content/plugins/ directory if you downloaded an earlier version. If you're downloading it for the first time, just copy it to that directory and activate it from the Plugin administration menu.