Depending on the level of the damage you might get away with a repair.
I have seen rims where chunks have broken apart and were still return to like new condition.
That's bad news, sorry to hear. Have a chat with these guys: http://maxpowder.co.uk
I had a wheel repaired by them some time back and they did an excellent job. Whilst I was there I saw a shattered wheel they were in the process of rebuilding - really incredible to see how they did it; building up layers of weld to the exact composition of the wheel, then machining back to get the OEM shape.
Thanks for the suggestion MAF. Certainly far cheaper. Do they guarantee their work? I may be behind the curve but have always been wary about the idea of bending alloy a second time.