I donate blood occasionally and I intend to keep doing so. However, not so keen on donating my marrow, can't see anyone needing my marrow especially, but if asked to donate it to someone, I might consider it. If the persons death would be worth postponing.
Organ donation is something I'm not really comfortable, mainly because I like my precious organs. I need them to live, but if needed doctor's can take them out of my cold dead body and give them to someone else. Recycle what can be recycled and burn the rest. I don't need any after I'm dead.
Finnish law was changed few months ago. Previously we had those donor cards too, but now everyone is a donor, unless they deny this. If the world would be a just place, people who opt-out donating their organs, shouldn't get any organs either.