It's a Cajon, which wikipedia describes as a box-shaped percussion instrument originally from Peru. You sit on it and slap the front, back and sides...it has drum snares on the inside of the light brown plywood side, for a buzz like effect.
I got it from my daughter and her girlfriend. (take THAT Rick Santorum!)
By the way, the pinkish edges on these pictures is a result of my iPhone case, which ALMOST fits. This is my reward for buying it on Ebay for, like, three bucks.
It really helps if you already know how to play a percussion instrument...which I don't....but I'm working on it. I went on line to try & find some video of someone who KNOWS HOW playing the thing, but it was all too intimidating. So as soon as I.T. Boy gets back to me, I'll post a video of ME playing it!