Panopticlick a project sponsored by the EFF to research web browser tracking, without using cookies or the visitor’s IP address. Here is the blog post on the EFF website. More impressive, here is the math behind the algorithm that the EFF is using for this project.
From the EFF: “When you visit a website, you are allowing that site to access a lot of information about your computer’s configuration. Combined, this information can create a kind of fingerprint — a signature that could be used to identify you and your computer. But how effective would this kind of online tracking be? EFF is running an experiment to find out.”
Now the obvious thing to state is that if a person changes computers or configurations change on the computer, the “fingerprint” would change (not making it a true fingerprint, similar to an IP address). However, as the algorithm points out, if you can equate the information to another piece of identifiable information, the server would be able to identify you.