I love it when games come out that reinforce information my kids are learning. Using a different mode to get the information across helps to cement that information in their brains. Plus, it doesn't hurt that its fun.
The website Playing History.org lists all sorts of places on the web where one can find history related games to play. Simply click on the topic on the opening page and you'll be directed to a list of games that fit that particular topic. Then, click on a specific game to get more information such as the website where its located, what grades its appropriate for, whether its free or not, the game length, and other pertinent information.
Problems with the site: Just be aware that the website, like this one, only provides links and has no control over any of the content you are directed to. Therefore, a little caution is merited and its always best to check out the games yourself before unleashing your kids on the Internet. Also, I noticed that there wasn't any new "News" since 2010 and some of the links didn't work. So, why even mention it? Because some of the information is still available and pertinent and more than I could mention myself.