OCCT (OverClock Checking Tool) will let you benchmark, overclock and monitor your system components.

It comes with four built-in test aimed at testing CPUs, GPUs, and Power supplies. OCCT also monitors in temperatures, voltages and fan speed, as well as system constants such as CPU Usage, Memory Usage, and FPS.
OCCT Features:

Up to 16-core support ( for instance, up to a Quad-Kentsfield or an Octo-Conroe )
Customizable tests ( Duration, Priority, CPU or RAM, ... )
CPU and Motherboard detection
Monitoring support through 3rd party application ( i.e. MBM5, Speedfan and Everest Ultimate Edition 3.50 or above )
Can produce graphs showing temperature and voltages during the test : Unique feature !
Multi-language support