Over the weekend, Katie really discovered her voice. Now, at random times, she will just open her mouth and start to either yell or laugh, or even do a sing-song type sound. The past two mornings, after she has eaten at 4:45 am, I put her back down in her crib and she just talks and talks to herself. Eventually, she will talk herself to sleep (I hope), but for now I stay in the room just until she drifts off.
Here is a video of me trying to get her to laugh yesterday (excuse my "fake" laugh - it's awful!).