Anthony Nolan is a charity set up to help save the lives of people who have blood cancer and blood disorders. They have set up a register to match people who, if needed, will donate their blood stem cells or bone marrow to people who need this transplant in order to survive. 
I will always remember the day when I first heard about the Anthony Nolan charity. We had a recruitment event in our assembly at school for the charity and we sat for around 20 minutes listening to a man talking about his young son who had a blood disorder and needed a bone marrow transplant to survive. Just as he was finishing his presentation, he revealed to us that unfortunately they didn't find a suitable match and that he son had died earlier in the year. 
That was the point that it really hit home for me. If he could stand up in front of a hall full of people and talk about losing his son, then signing up to the register was the least I could do.  In order to join, you need to be aged between 16-30 and you will register online and get sent a 'spit kit' in the post. As it would suggest, you spit in the tube provided, and freepost it back so they can test this and register you. To register see the Anthony Nolan Registration Page. How easy is that?
You may never be contacted if you are not a match, but you will stay on the register until you are 60. If you turn out to be a match, you will be contacted and talked through the process if you wish to proceed. Within 2 years of being added to the register, I was contacted to say I was a possible match for someone who needed a bone marrow transplant. In order to further test my suitability, I was asked to provide blood samples and send them back. A quick visit to the nurse later and my samples were on the way.
As the register keeps all details anonymous, I didn't know anything about the patient. In the end, the patient turned out not to be suitable for a transplant at that moment in time. Even though I didn't end up having to donate the bone marrow, the prospect that I could have possibly helped save someone's life was amazing and worth any effort from myself. To find out more about what the charity do and signed up to the register, see their website
Why not sign up to the register, you may end up saving someones life!