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...
Metropolitan Museum of Art
Metropolitan Museum of Art: Art of the Mughals After 1600
In addition to watching a slideshow of beautiful art commissioned under the patronage of the Mughals, read an informative essay describing the changes in styles under each Mughal leader.
University of California
Ucla: Manas: History and Politics of the Mughal Empire
This article surveys the Mughal Empire of India (1526-1857) and traces its origins, names its rulers, and provides historical illustrations and a map.
Khan Academy
Khan Academy: The Taj Mahal
The Taj Mahal is exceptional for its monumental scale, stunning gardens, lavish ornamentation, and its overt use of white marble. View pictures and read the history behind the Taj Mahal.
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.