A few of my favorites...
-Pole crunches (tucking the knees into the chest while holding onto the pole). You can intensify those in a few ways -- not touching the feet to the floor between sets, or lifting with the legs straight out or in a straddle V, or both! You also get some upper body with those -- make sure the arms are engaged. You can do them on a pull-up bar at home or the gym as well.
-Floor shoulder mount/plow exercise... you can imitate this without a pole too. Lay with the pole to one side of your head, grab on, and lift the legs straight up over the head to one side of the pole, then back center, then to the other side. Also do it in a straddle with one leg on each side of the pole, making sure to control the descent.
-Side crunches on the pole, good for obliques. Step to the side of your pole, hook the inside leg up high, reach the arms out to the sides/on the hips or overhead (more advanced) and tilt your torso toward the floor, keeping your hips facing forward, then come back up. I also like to do these just as a hold -- keep the arms overhead, lean out to the side as far as you can, and hold til failure. Like a side plank on the pole :P Students always hate this one lol
-Head/forearm/handstands!! Great for both core and balance. If you can't control your entry into these yet, work on balancing in them and controlling the descent. Play with leg positioning and try to straddle the legs down. They are fun and a great strengthener.