The EFF runs a very useful web-based service that estimates the uniqueness of the HTTP header lines that your browser sends to every web server from which you request a page or other content.
Many Panopticlick users have unique headers, even though the service does not pay attention to all information that a browser could provide.
Generally, the less opportunity your browser provides for running active content, the safer you are. Of course, this does not apply only to browser fingerprinting, but also to software vulnerabilities that can be used e.g. for loading so called drive-by malware.
Panopticlick exists at http://panopticlick.eff.org/.