PCSTATS Maximum Videocard Overclocking Chart
 

Overclocking is alive and well! PCSTATS has all the details you need to see at a glance to know how the various videocards tested perform relative to each other. The chart we've compiled below lists the highest overclocked core and memory clock speeds we were able to achieve while maintaining 100% stability.

http://www.pcstats.com/NewsView.cfm?NewsID=59944

I trust these numbers more http://www.hwbot.org/hardware.videocard.statistics.do
much more samples tested!