Isn't Google just the best. All I did was searched Grade 2 apps and here's the first bit that came up. I didn't have a chance to check them all- go figure. Technology information changes so fast, too. I bet by the end of the summer there will be tons of additional reviews.
Here's some helpful sites to check out reviews on those endless number of educational apps.
http://teachwithyouripad.wikispaces.com/Grade+K-2+Apps#Social Studies- many preschool-K-1 apps but it does go up to Grade 5
This site is beyond fantastic and a must to check out. Their subtitle is: A Community Effort to Grade Educational Apps---WOW. They even have suggested uses for the educational app. There's also tags so you don't have to search endlessly for specific topics. It's geared for K-12.
OK gotta go--I may not be able to find time to go to bed tonight!