If you are not already using Google Analytics on your website then it is well worth looking into. It provides enterprise level website analytics and reports and is completely free. It also allows you to track your little green plane campaigns further.  

little green plane enables you to link your email marketing campaigns to your Google Analytics system in order to trace how many hits to your site came from your email marketing campaign.
 
Google Analytics tracking within little green plane is only appropriate if you use Google Analytics to monitor your website statistics. By adding some tracking information to the email you can isolate the results of the email within your analytics account. With this feature enabled you will be able to see the traffic that is directly related to the campaign.
 
Why should you use it when little green plane tracks clicks and opens directly from the email? Because it allows you to derive what traffic has been generated by individual little green plane campaigns. 

Check it out here http://www.google.com/intl/en_uk/analytics/