WEIGHTED STANDING SQUATS
For weights you can use a chair, soup cans or milk/water jugs. First do a shallow squat, then a medium squat, followed by a 90 degree squat. Do this for anywhere between one to five minutes.
PICNIC BENCH JUMPS
A picnic jump at a park works best. In order to really be effective for skiing and snowboarding, the jump needs to be at least 15-18 inches high (stairs won't do it) and look a little daunting at first glance. Stand on the ground jump up to the seat. Then from the seat, jump on the table. On the table, jump high into the air. Jump down and do it over. Again, anywhere from 30 seconds to five minutes.
Use a Bosu ball, Dyna-disc or a couple of pillows stacked up. Barefoot, stand on it at alternate standing on one leg until you feel that endurance burn. If you're advanced, try it doing a one-legged squat. "It builds your ankle strength and core strength."