Back in 2009, I stumbled upon the Anthony Nolan Trust. This charity is responsible for maintaining a donor register potential for bone marrow and stem cell matches. Back when I did it, it required a blood sample being taken and sent to the charity to add your details to their register. Now it's even easier, they simply take a cheek swab (just like in the crime dramas). If you're from the black or ethnic minority group then it'll be even more imperative you consider joining this list as the demand far out ways positive matches found for such groups.
Click here for my poor attempt to raise the money it costs to keep me on the register.