I just popped out to post a letter and noticed the old moon in the new moon's arms. Also known as the earthshine, or ashen glow, it is caused by sunlight reflected off the earth onto the dark side of the moon. When this happens, you can see the bright illuminated part of the moon (the new moon) cradling the dimly lit circle of the old moon.
I wish I had a really good camera so I could take pictures of things like this. But instead I'm illustrating this post with a sketch of earthshine by Leonardo Da Vinci as part of his Codex Leicester, written between 1506 and 1510.