Another good tool is EVGA Precision X, which will tweak the GPU clock, memory clocks, GPU voltage, fan settings, which also allows you to set up to 10 different configuration profiles for overclocking settings. The interface is a bit easier on the eyes, but that's probably a matter of opinion. Other features include options for frame rate cap, and built-in benchmarks. If interested, you can download here.
ASUS GPU Tweak
ASUS also has an entry in the field of GPU overclock software, ASUS GPU Tweak. The main screen immediately presents you with a wealth of slider bars for core clock, core voltage, memory clock, and fan speed modifications, as well as diagnostic charts. A useful feature of the Tweak GPU is that it comes with a GPU-Z monitoring software, which offers an in-depth look at your card statistics and its performance. Other useful features include the ability to set custom hotkeys, as well as check for BIOS updates for your GPU. You can download it here.
ATI Tray Tools
ATI Tray Tools is a compact device capable of enhancing the capabilities of an ATI card. Working from the Windows system tray, this utility allows you to overclock cores, shaders, and memory clocks, hardware monitoring and stress testing. You will not have access to some features that are available with other software, such as vidcapping, custom fan profile settings, or voltage controls, which may be a deal breaker. However, for a compact program, it does a good job working on ATI GPU. Download right here.
Paseban has provided some tools for tweaking GPUs for additional performance, so you will need to run your graphics settings through multiple benchmarks to test its stability and performance. One tool you can use is Unigine Heaven. Unigine Heaven is an impressive graphics benchmark. You can also break away from the render preset track and explore the given world, allowing you to test rendering quickly and offer something more akin to realistic in-game performance.