Challenge your push up and add a row. This is a great progression of your standard push up that will add more demands on your core musculature and shoulders.
You need two dumbbells of your choice.
Start in the push up position with hands holding the dumbbell weights. Perform a regular push up, weight shift to one side and perform a row. Make sure you alternate sides and keep your hips level.
To make this harder, perform a push-up windmill. You will perform a push up and as you row turn your hips so you are in a side plank position. Make sure you alternate sides.
Repeat 2-3 sets of 10-15 repetitions.