StatCounter provides free customisable hit counters, visitor tracking and website stats for Wordpress.com (hosted by wordpress)

1. Sign up for a free account at StatCounter and follow the wizard
2. When it asks for your web page editor be sure to choose Wordpress.com (hosted by wordpress) from the drop down list
3. copy the StatCounter code (highlight + ctrl c)
4. log onto http://wordpress.com/ and enter your username and password
5. click "My Dashboard" in the top navigation bar
6. click "Widgets" under the "Appearance" menu
7. Under the "Available Widgets" section, click the "Add" link beside the "Text - Arbitrary text or HTML" option
8. A new "Text" option will now be added under the "Current Widgets" section - click this "Edit" link
9. Enter "StatCounter" in the header
10. Paste the StatCounter code (ctrl v) in the main text area
11. Click "Done"
12. Click "Save Changes"