Bodybuilding, Athletics

Plyometric drills (dynamic reaction drills) will improve strength. i.e. box jumps.

In the gym you could do the olympic lifts i.e. Squat, power clean and leg press (not one after the other tho!) looking to do around 3 sets of 6 reps for strength.

Emmettcre, EnduranceRun is right about plyometrics, and these can be performed at home, you can buy your own "STEP" and use it at home, or a box for jumping. If you are to go this route, be careful, since plyometrics can cause injury. Make sure you're in good shape beforehand and try to land on a soft surface if possible.

Additionally, you can also try:

-Jump rope, one-legged especially.
-Hill sprints - find a steep hill, try sprinting up it fast, then jog slowly down to recover. Repeat 10-15 (depending on hill length) times while maintaining speed. Once you have a good handle on this, alternate sprints with "bounds". Exagerrate your stride so that it's very long. In both cases you'll be using the balls of your feet to push off, which is what you'll use in your jumps.
-Lunges - lunge forward until front knee is bent at 90 degrees and rear knee is just above ground. Once you have a good handle on this, do them with weights (dumbbells in either hand). Once you have mastered that, move on to jumping lunges - do a lunge, then jump into another one. Lunges are great for generalized leg strength (perhaps to proceed plyometrics or other more sport-specific exercises).
-Calf Raises - find a step, stand at the edge of the step with the balls of your feet. Bend slightly at the knees. Lift your body upward by pushing your feet upward. Again, these are more for generalized leg strength, rather then sport-specific.

One final point, check with your coach if these exercises are going to supplement your training. Make sure not to over train.