Sorry I haven't posted in a while.
Here's a few more drills you can do to strengthen your ankels and literally make them un-sprainable.
1. 747's - This is a quick drill that you can do anywhere, anytime. Stand on one leg (keeping it as straight as possible) while putting your hands out to the side (that's why they're called 747's - you'll look like an airplane). First lean as far forward as possible, bending as the waist and keeping the balancing leg straight. Hold this position for 30 seconds. Now repeat this with the other leg. You'll repat this in each direction (lean forward, left, right, and backwards) with both legs, holding it for 30 seconds each way. It should be challenging to stay balanced (if it's not, you need to lean farther) and it's ok if stumble a few times. You'll feel a nice burn in the lower leg, around the ankles. This is a quick and very effective drill.
2. Toe Raises - As Jimmy Smith talked about in my previous post, most athletes have WAY stronger calves than they do shins. Beleive it or not, strenghtening your shins will not only strengthen your ankles, prevent shin splints, and balance out your lower leg musculature....but they probably will improve your vert! Shins are arguably even more important than the calves in jumping (not to mention running, cutting, deccelerating, etc.). Toe raises are pretty much the opposite of calf raises and, again, can be done pretty much anywhere. Just find a stair or ledge with something to hold on to for balance. Simply stand with your heels on the edge of the stair and lift your toes as high as you can and the down as low as you can, trying to go throught a full range of motion. Just try to do as many as you can while keeping good form.
3. Heel Walks - These are very similar to the toe raises (strengthens your shins). Just walk backwards and forwards, taking small steps and staying on your heels (pull your toes upward as hard as you can the whole time). Try walking 10 -20 steps forwards and backwards to start out.
Use these drills 3 - 5 times a week, along with some of the ones from my previous post and you'll be on your way to ANKLES OF STEEL.