Futuremark has just launched another interactive web based benchmark application called VirtualMark, that allows users to determine their 3DMark score, without actually running the 3D benchmark software on their system.
Once you allow the web application to run in your browser and analyse your system, it checks the ORB database for submitted results which match your system specifications as closely as possible.
It's not going to be 100% accurate but with the millions of results already in its database, you should be able to find a match which is pretty close.
Obtaining a common score is a simple three step process with VirtualMark which takes only a minute or so to run. Head on over and give it a try!