Box Jumps.php
Box jumps are nice and easy: get in front of a box (or chair, staircase, bench, or whatever else is solid enough to jump on top of), jump on top of it, and hop back down onto the ground.
Don't land with your knees locked, be sure to use your legs as springs to soften the landing and minimize the impact on your knees and other joints. Feel free to adjust the position of your feet before performing your next box jump. Proper technique prevents injuries, so it's better to take a second to not mess up your knees than to go berserk and hurt yourself.
If jumping on top of a box with two feet is too easy, you can try a single leg box jump, or go back and forth by jumping over it (frontal, or sideways). Or...get a bigger box!
Other leg exercises
Calf Raises
Jumping Lunges
Lunges
Squats
Squat Jumps
Star Jumps
Step Ups