I'm quite partial to hill sprints myself, given the reduced risk of sprain and the extra resistance. It also helps that I live on a steep hill. If you are going to do any sprinting, always make sure you are running on an even surface, or you are risking a sprain.
For strength, you want to accelerate to maximum speed as quickly as possible. For lactic tolerance, you want to hold the maximum speed for as long as possible On the flat, this may mean over 200m if you are very healthy - the top sprinters only start slowing down again in the 400m+ races.
TO EVERYONE - DO NOT GO STRAIGHT INTO THESE WITHOUT MAKING SURE YOU ARE PHYSICALLY STRONG ENOUGH AND UNDERSTAND THE CORRECT FORM, OR YOU WILL INJURE YOURSELF.
(Sorry for that, I just wanted to make sure that people read the disclaimer, as I don't want to be responsible for someone only reading half the post and giving themselves a serious injury.)
The best advice I can find is the first answer by 'TUnit' in this link: http://www.bodybuilding.com/fun/wotw27.htm
Generally, drop jumping is the classic plyometric exercise, but it is also one of the most difficult. They are only advised if you have decent leg strength (1.5 times bodyweight squat is often advised). Even then, you'll want to make sure you ease yourself into them, start with < 1ft drops just to get the technique right, then work your way up over several sessions.
If you aren't that strong, standing jumps and bounding are advised. For the former, stand on a spot, feet shoulder width apart, then 'explosively' jump as high or as far forward as you possibly can. Bounding is essentially jumping forward from one leg to another, kind of like an exaggerated slow motion running motion.