Wolfram Alpha

8. Wolfram Alpha ($1.99, universal)
Wolfram Alpha is now a much more affordable app than when it first came on the market. Those with an elephant's memory will remember that when it first became available on the App Store, it cost $49.99. It was later dropped to $19.99, then returned back to $49.99 At the beginning of April, the company dropped the price down to $1.99 for good, as well as giving everyone who bought it a refund.

On the iPad, the Wolfram Alpha app shines. This is the case not only for the results, which often contain large, colorful charts but also for the enormous, three-story keyboard that stretches out like a cat waking up from a nap. On the iPhone you need to scroll through three different sub menus to view all the keys, whereas on the iPad it's all there for you--all at once.