My favorite is the Lincoln Memorial Interactive from the National Park Service . This online interactive has amazing clarity, panoramas, and great video reflections from Park Rangers about the meaning and importance of both Lincoln and the Memorial.
|EarthCam of the Washington Monument|
For older students using primary source documents the Library of Congress Web Guide for Abraham Lincoln and George Washington gives students access to amazing research tools.
If your class is studying George Washington the Mount Vernon Virtual Mansion Tour is a fun spot to visit to see inside his home.
The History Channel has a nice history of Presidents Day with lots of fun links, from the evolution of the White House to our modern Presidents.