Dutchmarbel (sorry - no idea where your site is) says he wishes he (she?) could do more for the refusniks than " hang up a poster, write letters, have a banner on my website and tell others..."
Well, the quickest, easiest and one of the most important things to do is tell the boys your heart is with them. Just mail them email@example.com.
Of course they don't have email access in prison, but it will be delivered.
One of the things that helped me most when I did my time was the support I received from all over the world. Its not easy to keep your conviction and strength in these conditions. Its much harder doing a whole year in a civilian prison. Just let them know there sacrifice is not in vain.