Virginia Postrel has a terrific piece on organ donation in our pages. Long story short: don't count on cadaver organs, because there aren't enough of them, and organs from living donors last longer. We need quasi-market mechanisms to attract more living donors.
Postrel deals with "donor chains" in which people who want to give a kidney, but are incompatible with their target, form chains with other incompatible donors to get everyone what they want. Then she moves onto markets, which are very controversial. I confess, I don't understand the ban on paying for organs. We let eighteen year olds decide to go to Iraq in order to eventually pay for college, but we won't let a thirty-five year old sell off a part of himself that he probably won't need, and with which he could save a life?