Speed is a function of power and coordination. The more power you can generate to propel you forward the faster you will move from point A to point B. The more biomechanically correct you are, the smoother your movements will be resulting in greater efficiency. The more efficient you are the less energy you use, resulting in increased ability to sustain faster speeds over longer distances. The agility drills section will also help increase your speed.
Drill #1 - Front Lunge
With your feet together and your hands on your hips, step forward with one foot while bending the knee until you're in a lunging position and the opposite knee is 6-9" off the ground. Push off the front foot and return to feet together position. The degree of effort can be varied but the amount of force you use to go forward and back. Repeat with your other leg. Do 5-10 repetitions per leg.
Drill #2 - Side Lunge
With your feet together and your hands on your hips, step sideways approximately 2 feet with one foot while bending the knee until you're in a lunging position. Repeat with your other leg. Do 5-10 repetitions per leg.
Drill #3 - Step Ups
On a step or bench, step up with one leg and follow with other leg. Step down with one, and follow with the other. Start off at 5-10 repetitions at a time, you can add repetitions and eventually weights.
Drill #4 - Frog Jumps
This is like a broad jump -- it's an explosive dynamic movement. Stand with both feet together and jump as far as you can. To start, do one jump at a time. Add more jumps to challenge yourself.
Drill #5 - One-Legged Frog Jumps
This drill is the same as above but instead, you use one leg. This drill is slightly more advanced since you are putting all the forces into one leg instead of two. Do shorter and smaller jumps, but more at a time. Start off with 5 jumps on each leg, and progress from there.
Drill #6 - Slalom jumps
When you first start doing these, do very small lateral/forward jumps with feet together. These can be done one at a time or in multiples like you're skiing.
Drill #7 - Stork stand
Stand on one foot, bring one knee to your chest. Hold position and maintain balance. This is a good ankle and balancing exercise.
Drill #8 - Fast feet
This drill can be done while running or standing in place. Rise up onto your toes, run in place (or run) on the tip of your feet. (This drill simulates jumping rope, without the rope). Do not lift your feet more than 1 - 2" off the ground.
Drill #9 - Fast feet ladder drill
Place 10-15 markers (anything that won't blow away and you can easily see) about 15 inches apart. Get a running start and run placing alternating feet between the markers (like climbing a ladder). Lift your knees higher to go slower, keep your knees low to go faster. You can alternate between high and low knee lifts for each pass. Start off with two repetitions, and increase from there.
Drill #10 - Skipping drill
Basic skipping can be done in slow motion (walking) or at a faster speed. There are many variations of skipping such as explosive knee lift, blocking of the thigh, short hop on opposite foot, snap foot down to ground in dorsiflexed position, repeat with other foot. This can be a slow, forward moving drill or have various speeds and movements.
Drill #11 - Bounding drill
This drill is a high skipping movement, bounding high in the air off one foot. These are often done best on hills with moderate inclines.