Encyclopedia Titanica - Excellent site with lists of passengers, crew, lifeboats, cabin assignments, deck plans, cargo list, and much more.  The passenger list is active and will tell you information about each passenger including pictures of some and whether they survived.
http://www.encyclopedia-titanica.org/

Titanic Archives
This site has both the history ot the Titanic as well as information on it's discovery.    http://www.rmstitanic.net/titanic/index.html

Discovery Channel site that shows the interior of the Titanic as well as video of the expeditions by submarines to the wreck of the Titanic. Includes multimedia highlights and a tour of what the ship was like before it sank
http://www.discovery.com/stories/science/titanic/titanic.html

How Deep Can They Go?  This site shows video of her final resting place, some  excellent links to more information.
http://seawifs.gsfc.nasa.gov/OCEAN_PLANET/HTML/titanic.html

I will add more sites as we find good ones.  Many of these sites have additional links, but the majority of sites are personal web sites on the Titanic and may contain inaccurate information.
 

       If you are really interested in the Titanic, you might want to make a trip to Cleveland, OH where one of the three Titanic exhibits is currently on display.  I have seen two of these exhibits, one in Chicago and one in Memphis, TN, and both were slightly different and had different items that had been brought up from the wreckage and debris field.

Great Lakes Science Center
March 2, 2002 - September 2, 2002