We Are Teachers is a great resource (and it's free). Sign up to get the latest cool tricks, ideas to make your classroom come alive! Here is a blog that lists 60 great apps (many you have seen or heard of) to use with ALL grades through science, tech, art and math lessons. Apps are organized by level and subject area.
Socrative is a smart student response system that empowers teachers to engage their classrooms through a series of educational games and exercises via smartphones and tablets. Our apps are super simple and take seconds to load and run. Teachers control the questions and games on their laptop, while students respond and interact through their smartphones/laptops.