Here are some apps that could be helpful for doing your schoolwork. I have Apple products (iPhone, iPad), so that's where I have found them. If you are interested in helping me compile a list of apps for other devices (Droids, etc.), then please feel free to let me know!
Search in the app store for...
Dictionary
Flashcards+
Kindle
Free Books
FreeSaurus
Currency
Units
Goodreads
Constitution
Capitals
Coin flip
AccuWeather
Google Earth