Teaching Appz is a cool site I learned about on Twitter from my PLN last week. I've been exploring it and I've found some great apps.
The site has educational apps sorted by Subject Area, Age Range, and Device/OS and a category just for teachers. You can also search the site.
The apps are reviewed and are really good. You can also submit apps to the site.
If you are looking for apps for education, this is a good place to start. http://www.teachingappz.co.uk/
Mobile Apps and Resources for Students and Teachers
Android for Education - resources, apps, tips, and more.