Stand with your foot flat against a wall, so that only your heal is touching the ground, and lean into the wall.  Then stand so only your toe is touching the ground and lean into the wall.  Keep the other foot flat on the ground.  Then switch sides.  It stretches your calves, but also works for me on shins. 

And they have these little plastic contraptions that are rounded on the bottom, in a half circle shape that mimic the same movement, wich actually work better for the shins, because you can get a better angle leaning forward on your toes than you can using the wall.  I've seen them in gyms, but have never seen them in a retail outlet, so I'm not sure where to tell you exactly to buy it.  You could probably find something similar at a sporting goods store.