You could use Piwik, which is a Open Source Web-Analytics Software (http://hubpages.com/hub/Web-Analytics-with-OpenSou... or use Google Web-Analytics.
IMHO it is most important to define what the Success of the Marketing Campaign should be. Thus it could be to have subscribers to your Mailinglist or Buying a product or what ever you define. Set a number for it, which should be reached within a specific period.
It might be that the Success of your Campaign would be a failure for another business. This is based on a different definition of Success.
Hope this helps.