The real game changer, when it comes to sport-speed isn't how fast you can accelerate, but how fast you can decelerate. For team-sport athletes, there is nothing linear about what they do. Games are dynamic and you are very rarely running in a straight line with nothing impeding your progress. So why deceleration important?
Deceleration (or "breaking down") is what allows you to make cuts or to stop (duh). Straight line speed is great, but you will eventually need to go somewhere else. If you can decelerate and change directions faster than the next guy, you're going to be a better athlete. This is like a wide-receiver running a route. The corner back who is playing defense on him is going to be just as fast as he is. But if that WR can stop on a dime, change directions and go full speed before the defense, he'll be open and will have an opportunity for a catch.
How can you work on improving deceleration? Here are some great drills.
Heidens (or skater hops) are a fantastic lateral movement drill. The idea is simple: start on one leg, explosively jump to the next and athletically stick the landing. Without putting your other foot down, jump back to where you started. This drill will help improve several things: proprioception, single leg stability and power-development.
The most common drill to teach someone how to decelerate properly is the Depth Drop. It's a more advanced variation on the box jump, because rather than avoid the eccentric stress of landing (as in the box jump) you are actually only training the eccentric portion. Make sure the athlete lands athletically, and with your female athletes make sure they stick the landing with their knees OUT.
A nice progression of the depth drop is the 180 Depth Drop. Start off facing backwards, so that when you land you have to resist the rotary forces you've produced.
Depth Drop Lunges are a really cool drill I picked up from Mike Ranfone a while back. Start off on a medium-height box facing sideways, drop off the box and stick the landing in a lunge position. This drill is going to teach you to absorb your body weight in a pretty athletic position.
These are just a few of my favorite drills to help teach people how to get fast and explosive. Try some of them out and let me know how it goes! Have a great day and go lift something heavy!