i'm a huge fan of glute/ham raises! i used to have very weak hamstrings and it was effecting my play, then i incorporated these into my workouts. huge differance, and they helped my deads, squats, and sprints out a great deal.
here's a link:
http://www.kvusa.com/wl/floorghr.htm
the above link shows them from the floor....if you can get your hands on the machine (looks similar to a roman chair) then definitly do it, if not, the above work very well too.
good luck in your training.
cheers