Incline Bench but very light.
Come down to just below the chin almost to your throat. Pause for 3 seconds or so and then press back up.
Do this for 12 reps or so.
If you angle your chest so that it is almost running parallel to the floor you will notice a nice stretch in the upper pecs.
That was a lagging part of my chest for me...and this is how I fixed it.
I actually picked it up from a buddy who used to be 'shoulder dominant' and he pointed me in that direction.
It's basically just forcing you to use your chest instead of anterior deltoid to move the weight.