American History Timeline is a wonderful free iPad app that focuses on American History from 1770 to Current Events. This interactive has 100s of images and tons of information that can be sorted through. Best of all their are educational games such as Scramble and Matching to help reinforce learning.
Historia is a new (beta) site that is beta-launching this Winter that is ideal for bringing History into the classroom through Game Based Learning. This game has students team up in groups to lead a civilization into prosperity by doing project based research and making important decisions that impact how their civilization will grow. Also, this game is designed for all kinds of devices such as: interactive whiteboards, tablets, and desktops (Mac/PC), and is aligned to Common Core Standards.
Time Machine: Age of the Emperors is a excellent educational iOS eBook that is free today. This is an innovative digital book that is great for History teachers that is highly interactive for students. The way this works is a user creates a profile/character and then makes decisions as they explore different ancient emperors and civilizations. The choices they make affects their progress throughout the book and best of all it saves their progress as they go along.
Basher's Presidents is an iOS app I had the pleasure of coming across today. This is a super fun educational app for learning all about the US Presidents. In this interactive app students can view a flipcard on each president which explains a little bit about the president as well as one quirky fact. Users can also partake in a timed game in placing the presidents in the correct order. Other nice features is the ability to vote on your favorite president and order a book on the US Presidents.