Simple Bracket is an iPhone app by Studio Neat for filling in brackets for March Madness and competing with your friends and family. What makes Simple Bracket special is it's easy-to-use interface and sophisticated scoring system.
The folks at Studio Neat partnered up with mathematician Dr. Ted Gooley, to implement what they claim to be the "most statically sound bracket scoring method available today." Simple bracket also awards achievements and badges for certain outcomes, like winning a game by a buzzer beater.
Unfortunately, Simple Bracket requires a Twitter account to use, but if you're ok with that and a big March Madness fan, you should pick this one up!