I just donated blood last month. I tried to donate two pints but my vein got infiltrated so I couldn't. I think that everyone who can and is not needlephobic should donate. I makes you feel good that you are helping someone.
I am a regular blood doner and have been for almost 10 years now. You can donate every three months and i do so without fail. The way i see it is it only takes 30 minutes of your time once every three months but look at the lives you can be saving!!