The Bicycle exercise is a good move for the abs and obliques:
Lie face up on the floor wiith your hands clasped gently behind your head. Bring the knees in towards the chest and lift the shoulder blades off the ground without pulling on the neck. Straighten the left leg out to about a 45-degree angle while simultaneously turning the upper body to the right, bringing the left elbow towards the right knee, and then switch. Continue to alternate with lots of control.