The Lagom LCD monitor test pages
 

With the first few test images, you can calibrate your monitor by adjusting the brightness, contrast, clock/phase, sharpness, and gamma settings of the monitor. I recommend to go through them in the order they are presented. If you use this page in a shop, don't assume that the contrast and other settings are at reasonable values before making a judgement. The images are best viewed in a dim or dark environment and in full-screen mode. In most browsers, F11 switches to full-screen mode. If switching off the lights is not possible, try using a piece of cardboard to shield environmental light.

If you have any kind of color management system active in your operating system or video-card driver, then disable that first. First make adjustments to the monitor settings to let it behave as close to the ideal as possible, and only after that you can use the color management to compensate for any small deviations that remain.

Actually, calibration is not really the correct term. Calibrating a monitor would mean that you measure the response of the monitor and then compensate for non-ideal behavior elsewhere, for example in the video-card driver. Here, you are supposed to change the properties of the monitor itself to let it approach the ideal better. But then, who cares whether you call it monitor adjustment or monitor calibration...

http://www.lagom.nl/lcd-test/

A site worthy of a bookmark :)