Generally to become a bone marrow donor it costs a fee that covers the cost of the test kit used to type you for donation. During this drive registration is free for the first 10,000 people to register online and the first 36,000 people who register in person.
They have an especially dramatic shortage of minority bone marrow donors. Please spread the word.
Turns out I don't qualify to donate - deferred due to chronic back and neck problems. But you may be able to.