Today's official Free App of the Day is Run in Crowd. But, frankly, it is so poorly reviewed that I just can't recommend it and I suspect Amazon will rethink it and offer something else later in the day. If they do, we'll announce it.
So, today, I'm offering a KindleBoards Alternate Free App of the Day: Bubble Shoot
This is a classic "match three" type of game and well reviewed, with 99 five star reviews out of 114! It has an arcade mode, a puzzle mode and over 270 levels. Have fun!