I bought Poker Odds Calculator Pro for my iPhone for $2.99 a little while back and really liked it. It’s not a simple odds calculator, it’s like PokerStove, with the ability to calculate odds against a custom range of hands, random hands, and a set of pre-defined ranges. It was just updated; the new version speeds up card entry and lets you drill down into all the various permutations of winning hands. I can’t recommend it enough, because for May 27, to celebrate the opening of the WSOP, developer Richard Mullinix is giving it away for free.