Regarding Baby - What Is Play?: "Play is the way children naturally explore, and the way they gain and practice skills they will use for their whole lives. BUT play is not done to attain any reward, or end goal. Children gain pleasure from engaging in play, and this reinforces their desire to play more." (This post is full of great quotes.)
Not Just Cute - Build Executive Function: "The good new is that many researchers believe that these self-regulation skills can be increased through practice and experience. Perhaps the better news is that this often takes the shape of play!" (This post has great information and great ideas to put it into practice.)
Hands On: As We Grow - 30 Days to Hands on Play: "Learn to play with your kids! Ideas to get you out of the regular old routine. The rest is for you to decide." (This post is really a series of posts from Hands On: As We Grow and The Imagination Tree, a challenge to play every day.)
So go out and play today!