Stumbled upon this little experiment/test being run by Harvard.

http://kgajos.eecs.harvard.edu/ag/

It's a set of "click on the colored circle" test. Once the 9 sets are done, it will guess your age based on a myriad of factors. It came pretty close to my age- I figure it was off since I am pretty tired today. I hope it was off because I am tired today and not that I am prematurely 6-12 months older than I am chronologically.