This calibrator receives a favorable review from MaximumCPU, it's easy to use and provides excellent results, but the cost may be prohititive for casual users.

"DataColor’s Spyder color calibrators have been a godsend for accurately calibrating screens for years without resorting to expensive calibration services. The “Spyder” contains a small CCD camera that measures the output of your display as the accompanying software adjusts the color profile. The Spyder3Pro offers additional functionality like a larger sensor, improved software, and the ability to sense ambient light and adjust to changing light conditions."



Link: Maximum CPU