The World Factbook is a highly recommended iPod / iPhone / iPad app for social studies and geography teachers (primary and secondary).
It includes extensive information on 250+ countries around the world, including maps, flags, geography, demography, government, and so much more. This app is a fantastic resource for student research, and is available entirely offline – NO WiFi required!
For: Teachers, Students (Upper Primary – Secondary)
Cost: $1.99 (Download)
Requires WiFi?: No.