The FDA's guidelines for blood donation state that you can NEVER give blood if you:
Are a man who has had sex with another man since 1977, even once
Have used illegal drugs with a needle, even once
Are a man or woman who has had sex for money or drugs any time since 1977
These rules, designed to protect the blood supply from HIV, are discriminatory against whole classes of people, and miss the point entirely. HIV doesn't care WHO you are, what matters is what you DO. HIV is detectable in the blood six months after transmission; a person who has been clean from drugs since the 1980s and never once shared a needle is at a much lower risk of being HIV+ than a heterosexual person who just had unprotected sex last week.