This is a great geometric and spatial reasoning $0.99 app for both iPad and iPhone. In Slice It!, you are given a figure and a certain amount of cuts to make equivalent fractions. There is room for error, and at the end of each level you are told how close you were to perfection with the actual percentage of your cut-up shapes shown.
Of the many apps I have explored this summer, this game appears to be the most ready to be introduced into a middle school math class. The feedback is immediate, the muic is fun, and the interface (simulated graph paper and pencil) is extremely accessible.
Header photo by Robert S. Donovan