http://www.marrow.org/

You can sign up right now (well the first 10,000 people) to have a self-testing kit for the ability to become a marrow donor. As someone who knows someone who has benefited from this, I think it's something we can each very easily do that can really help. They'll mail you a few swabs to take sample from your cheeks for tissue type and then if matched, will contact you for your help. I'd encourage everyone to get tested.