Yes Ati-Tool is a very good program to help overclock a GPU
It allows such features as
-Finding the Max Memory, GPU Clock, and Shader
-Scanning for Artifacts
-Heat Monitoring
-Overclocking Profiles
-Startup Options
I love it, A great tool to bump up a little performance in you video games, I get a 5 fps increase in Day of Defeat with a 20% overclock.