The best way to calibrate a monitor is to buy a Spyder3, Eye One or similar device. Don't bother with the Adobe Gamma that's built in to Adobe software. It sucks.
There is a free software called QuickGamma for Windows users that is better than Adobe Gamma, but it's still not as accurate as hardware based colour correction.
http://www.softpedia.com/get/Tweak/V...ickGamma.shtml
http://download.cnet.com/QuickGamma/...2_4-53184.html