A D3D test that is commonly used is 3DMark2003, which you can get at www.futuremark.com
. A lot of the websites use it in their reviews even if it really isn't a great measurer of real gaming performance.
Lots of games these days have benchmark capabilities built into them. For example, if you have Quake 3 with the 1.32 patch loaded, you can type the following at the console by pressing tilde (~) to get a benchmark score:
/s_initsound 0 (to disable sound)
This will run through the demo included and then exit back to the main menu. Pressing tilde again will show you the framerate.
Other games have their own ways of doing benchmarks. These are really the best, since they're the actual games, and not some synthetic benchmark.