http://www.techpowerup.com/downloads/SysInfo/GPU-Z/

Works for both AMD and nVidia.

The program is called GPU-Z and if your card has sensors (most gaming ones do) it will display them for you. So you can monitor GPU load just as if you would CPU load. For WoW, GPU load is almost always the bottleneck as long as you have 3+ gigs of memory. Try it out and post your results!

Also check out Riva Tuner as well - it can graph it out.

http://www.guru3d.com/index.php?page=rivatuner