I recently came across this website called BloodHelpers Where you can register and people who need blood can contact you for blood donation.
I think this is a wonderful concept which can help the people looking for blood donors. It is a very troublesome process looking for donors of specific blood type in emergency situations. And having such a resource center is definitely a boon for the people in need.
I've registered there and I request all of you to go ahead and do the same.