Variety is important in training your entire calf muscle to do what you want it to do. What I mean in saying that is that strength via weight is absolutely essential but if you want to gain speed then you must be doing sprint work, and if you want to jump higher then you need to be jumping.

My favorite calf exercises are:

One Leg Calf Raises

Standing with your toes of your right foot on the edge of a step perform a calf raise by raising your body on to the tip of your toes then slowly lower yourself until your feel drops below the level of the step. Use a handrail to assist your balance if required but do not use the handrail as leverage for the exercise. Perform this exercise slowly for best results. After you have completed your right leg switch to your left and perform the required reps. Once both your right and left leg are completed you have done 1 set.

Dumbbell Calf Raises

Stand with your back straight and your feet flat to the floor shoulder width apart and tows pointing forward. Holding two dumbbells, perform a calf raise by raising your heels off the floor as high as possible keeping only the tips of your tows on the floor. Lower back slowly to complete one rep.

Ankle Jumps

Stand with your hands by your side with your feet shoulder width apart. Using only your ankles elevate just 7-8cm/3 inches off the ground. The objective of this exercise is to ensure that your jump reaches the required height but to complete the repetitions as quickly as possible.

And don't forget your 60 yard and 20 yard sprints.