i have found these very useful and the players certainly enjoy them:
car pushing- have teams of three push cars for say 30 meters, racing against other teams of three.
tug of war- just need 15-20 meters of thick rope
fireman carrys- easy to apply, tough to do!
if you can get hold of some heavy medicine balls or equivalent, these can be great for throwing exercises
and as ash mentioned, any form of wrestling/grappling is great for contact conditioning.
hope this helps!
cheers