Digital History for America

There are many web sites for history but few as all-encompassing as

http://www.digitalhistory.uh.edu/

This site focuses on U.S. history and does it very well. It includes a full online textbook (free), many documents, images, and media (all free). Plus it is just plain fun to read tests like this one:

"Could You Pass the 1885 Admission Test for High School?"

Definitely worth bookmarking for the teacher (or student) who might need to grab something for class.