I play college football currently and went through the mess known as the recruiting process. I dropped about .2 off my my 40 time by stretching 2-3 times a day for 20 minutes and doing sets of straightleg deadlift with 70-80 pounds (or whatever is a sem-light weight for you that will create a burn) for 30 reps for 2-4 sets all during my junior year.
At the Nike camp I went to I also learned alot of good plytometric excercizes. One basic one you can try is doing 4 sets of 10 reps - while holding 15-20-25 pound weights down to your sides, bend down in a squat position and jump as high as you can. After completing the sets, do 2 more sets with no weight for 20 reps. It will burn your hammys/theighs if you are doing it correctly. Most of the time, the pople with the fastest 40 times are also the people with the highest vertical jump.
Another important drill is the shuttle run. PRACTICE this and it will increase your side to side speed (also they use it in most football combines). Place 3 cones in a line 5 yards apart from each other. Next stand 1 yard away from the middle cone with the other cones to your left and right. With you hand perpendicular to the middle cone, sprint to the right cone and touch the "line" sprint back across to the far left cone and touch the "line" then sprint back through the middle. Have someone time you during this, good times for an inside linbacker (what I played in high school) are about 4.5 seconds (or on average .2 faster than your 40 time).
Practicing your start is vitally important in timing, it can save alot of time. Make sure you arn't false stepping.
GOOD LUCK.
<message edited by hardwork86 on Monday, January 09, 2006 10:26 PM>