For those who wish to serve others, one can be a living donor of bone marrow. There are restrictions--I could not join the registry because I have mitral valve prolapse. Most individuals are no so restricted.
It's easy to be added to the list--all they initially need is a sm. sample of your blood in order to test for certain qualities to be matched. If you should be a match in these areas, you will be called back in for more sophisticated testing.
One word of warning: the removal of healthy marrow is painful, but not excruciatingly so. I would urge everyone on this forum to consider this.