Classkick

http://www.classkick.com

This is a website that I reviewed and I would love to have this in our school system.  It is easier to identify those students who are completed and those students who are struggling and you can give them one on one help without anyone knowing and embarrassing them as you help them on their iPad.  This would also show growth and weaknesses and help with assessing where the students are in that area. 
I would use this in my classroom.  Easy access, standard based materials, core curriculum alignment. It is easy to use and does require accounts for student access.  You can use any grade and any subject area. 
You can create all kinds of projects: math problems, story problems, art projects, etc.  Just listening to the teacher share about the website she was excited and very motivated.  It gives the students hands on and an opportunity to focus and not be lost by lectures.  The teacher is freely moving around the room helping whoever needs help.  She can watch everyone and help those who are struggling to get on the right track. I simply love it!!!