As much as possible.
Here're some more ways to help out in Haiti, besides, of course, donating to the We Are the World Foundation. You can download "We Are the World for Haiti," too.
Now of course, concerns of child trafficking out of Haiti continue to grow. So don't entertain any fantasies of adopting any Haitian children until more civic infrastructure has been rebuilt. The best thing you can do is help in other ways.
But another issue still remains: sexual abuse and molestation here in the US.