Audubon Birds: A Field Guide to North America, originally $9.99, is today's free app. This is an app for the birds watching connoisseur. Word of advice, the initial download is about 13mb. But it has an additional (although it's only optional) hi-res picture file download that's over 500 mb.
Word Grid Solver, originally $2.00, is today's free app. It's an app that helps you find words in Scrabble games, or other word games, to give you the highest score possible. It let's you input your rack of letters and the board. Very useful at the local Bingo Hall!