Just a couple videos I found on the internets that you may want to consider adding to your programs. This would be a great drill to work on your reaction time, balance, and quickness. If you're having trouble with your random gate starts, this might be a way to help you react when that light comes on.
Below is another good article on improving foot speed. This is a very important quality to develop, to maxamize the power in your sprints. These exercises would fit in well at the gym, after your warm up and before your plyos and lifts. Also a good drill to do when your outdoor sprint sessions get rained or snowed out.