Running on sand. You might want to start with wet sand. And then build your way up to dry sand.
Toe hops. Imagine jumping rope without using a rope. Gently and rapidly hop on the balls of your feet, focusing all of your effort on your calves/ankles. Your knees should be slightly bent, but should not be doing any of the work. I like to do these while holding a couple of 45lbs dumbbells (or plates) in my hands.
Thanks for the input guys. That article was interesting, and it kind of describes what I'm going through with one ankle, the sprain resprain thing. I recently put a more supportive insert in my shoe and I haven't had any more problems. However, I still land funny on it. The other ankle, I haven't sprained, but I'm still wobbly on it. Running on sand's not really possible here, but I might be able to intergrate it if I get to the parents' for a weekend.
Apparently one of the best combination warmup/exercises for the ankle is to lie on your back, stick your leg straight up in the air, and rotate the ankle 20 times in one direction, then 20 times in the other direction. It loosens up all the ligaments and muscles in the area, and strengthens them too - it's a tiring exercise, but you can do them every day, and it's supposed to be great at strengthening the ankle - especially the exterior.