In reply to HikeandClimb:
As already mentioned, be ready to expect a lot of muscle wastage when the cast comes off. The best thing you can do now, would be to try your best to move and stretch your fingers to help them heal.
I broke my wrist in august last year, and to be honest its now back to 85% of its previous strength, I'm climbing terms it seems to be my left bicep that is holding me back on locks off etc..
To help your hand heal, make sure you see a physio at least once and stick with the lots of stretches. Things like, stretching your wrist back as if praying, forward, and rotating, opening and closing fingers, and spreading fingers. Stick with this and flexibility will come back, get your self a squeaky ball and then a light finger grip trainer like the www.prohands.net/
For the time being, you could do lots of core exercises, leg raises, calf raises, sit ups etc and any other similar exercises. I find that i can do pull ups no problem, but push ups hurt as that position is similar to how i broke my wrist.
Good luck and have a fast recovery.