They never want my blood (damn anemia). Please make sure you inform your family in writing if you plan to donate your organs. Unfortunately, signing the back of your license means very little:
"Contrary to popular belief, signing a donor card or your driver's license does not guarantee that your organs will be donated. The best way to ensure that your wishes are carried out is to inform your family of your desire to donate. Doing this in writing ensures that your wishes will be considered. Hospitals seek consent of the next of kin before removing organs. If your family knows you wanted to be a donor, it makes it easier for them to give their consent.
A signed donor card or driver's license provides proof to your family that you wanted to be a donor, but these cards often aren't readily available.
They also aren't usually legally binding. Signing a state or national donor registry is helpful but provides no guarantee that you'll be a donor.
Registries aren't always checked and aren't legally binding. Again, the best way to ensure that your wishes are carried out is to tell your family that you want to be a donor.
If you have no next of kin or you doubt your family will agree to donate your organs, you can assign durable power of attorney to someone who you know will abide by your wishes. A lawyer can help you prepare this document."
http://www.mayoclinic.com/health/organ-donation/FL00077
I am an organ donor, plus I have given consent for my body to be used in a chiropractic school. I went through gross anatomy. I know I wouldn't have learned without a body to dissect.