The Junior General project is one that teaches students about military history and strategy by providing various simulations using historical miniatures (paper or plastic toy soldiers), maps and counters, and matrix arguments. The simulations are designed for middle school students.
These archives from Yale Law School include links to various primary source documents from the September 11 terrorist attacks. The Avalon Project gathers various documents dealing with Law, History and Diplomacy which could be very useful when discussing history, or current events.
The site includes photographs, pictures, sound files, and bibliographic citations from people who experienced various historical events. The site could be really useful in making lesson plans as well as giving students resources for assignments or projects.
This website updates everyday with information about an event that occurred on that particular day in history. The database it comes from, Beyond the Headlines, also includes various websites with interesting information that cannot necessarily be found in popular media or journalism.