Plymetrics, plyometrics, and more plymetrics....
They have upper body plyo's too, there done with a medicine ball. They are fantastic.
I personally love deadlifts too as well. Nothing will get you in kick ass, strong as fuck shape to drive the lane and slam into people the way deads doo. And deads won't wear your arms out the way pressing movements do, so you can keep them up during the season.
Upperbody strength will translate into lower body quickness. remember, you run with your arms as well. There is a reason why most skinny boys shoot terribly come 4th quarter - there arms are worn out.
And don't be afraid to add a little bulk, but I would be carefull though your walking a fine line. You can increase your strength dramatically by gaining as little as 10 pounds, as long as its lean muscle tissue. Depending on your starting weight though.