PBS
Pbs: Taj Mahal: Memorial to Love
A great website specifically about the history behind the Taj Mahal. (Has audio cuts that can be heard by downloading RealAudio.) Also has a wonderful timeline that chronicles The Mughal Dynasty. Be sure to check out the "education" link...
Other
Taj mahal.org: Taj Mahal
A series of short articles on the famous historical landmark in India. Includes a history, interesting facts and legends, tourist information and more.