Mozilla Collusion is a new Firefox browser add-on that helps you track which companies are tracking you on the internet as you browse various websites for behavioral targeting purposes. How it does this: Whenever Collusion detects some data is being sent to a behavioral tracker, it creates a red (advertisers), grey (websites) or blue dot through its visualization and also shows how the sites you visit and the trackers they work with are connected.

Check out Collusion here