Best Software to Test Graphics Card?

I use all this:

1- 3D mark 06
2- Lightsmark 2007
3- PerformanceTest (all you system)
4- Video Card Stability Test

IMO, the 3 is really good, test all your system or a component individually, and you can compare with rigs like yours.

I use

3D mark 06
3D mark Vantage
Furmark

I understand that 3Dmarks are for benchmarkings, but it's a good way to test out ur card
while getting benchmarks, to test my temps and clocks at 3D rendering

Next is Furmark, which from my understanding is probably the easiest way to test ur cards
overclocks and stabibility
It has temps, clocks, and it still renders in the backgroud while u change ur video cards clocks
You can change ur clocks and watch the furmark run, and if there are rendering problems such as
Furmark not processing normal graphics, therefore u can test your max stable overclock
It stresses 100% and there is an "extreme stress mode" which I never used

Hope this helps, and please correct me if I am wrong