I found this site last night it tests your reaction time. Found its a lot easier with a delay box, in my case .040 delay posted 3 .500 RT out of 10. too many red lights without.

enjoy
http://www.staginglight.com/services...hot/index.html

Looks cool, but CAN"T PLAY!!! only runs on win 95 OR NT4.0. I still run win 98. darn it. oh well. I have found this on in the past. It'* on my local dragstrips website, the've got reaction time tester and all kinds of HP and 1/4 time estamators.
Enjoy!

http://www.greatlakesdragaway.com.htm
http://www.greatlakesdragaway.com/sportsman.htm

Damn, the closest I got so far was .51 like 4 times!!

hit .50 my first 2 trys then took me about 15 minutes to do it again..beginners luck I guess