Houghton Mifflin has made its full-text Reader’s Companion to American History available at no charge online.
It contains the following titles:
+ Reader’s Companion to American History
+ Reader’s Companion to U.S. Women’s History
+ Reader’s Companion to Military History
+ Encyclopedia of North American Indians
+ Ships of the World: An Historical Encyclopedia
+ Civil War Battlefield Guide
+ Great American History Fact-Finder
Although the site can only be browsed, ResourceShelf offers tips on searching it with Google or Yahoo.