Free Online Government Textbooks

I've been waiting a while for FlatWorldKnowledge to come out with its second half its AP US history books which you can now find here.  The first half of the e-book is here.  There is no catch (they hope that your students will want to pay for the paper copy) and the books are very good and also have lots of pictures and are very easy to navigate.  If you want to save money for your school, then check it out as a regular or supplemental book.

I should add that here is a standard level one originally put out by Beyond Books and then the Independence Hall Association.  It too is very easy to navigate.

Finally if you want to combine video with text then the US government books (both AP and standard) put out by HippoCampus are excellent.