One of his favorite things to smile and laugh at, and even talk to, is a light-up musical toy on his Under the Sea Gym from Uncle Joey & Aunt Meg. He can be content under there for a half hour or more just looking around and smiling and talking to the animals on his gym. Needless to say, it's the best place to try and catch a smile...
He smirks
And looks at me with big inquisitive eyes
But we haven't caught a picture of him smiling on his gym yet.
I caught him laughing another time after a bath
And again after a diaper-changing (hence the unbuttoned sleeper)
You can sorta see it here- He does Stephen's side smile.
I caught a belly laugh on my cell phone

And finally a great smile picture, although not the greatest quality. Hopefully there will be many more of these to come...and documented with the good camera!