I gave blood a few times via Red Cross blood drives. It would be nice to be paid, but hey, it feels like charity to me.
I stopped because the years of Red Cross calling me got way too annoying after I moved. They kept calling from an area 6+ hours away to inform me of local drives. I asked to be removed from the call list and the lady got angry and refused. On a call later that week, I asked the guy calling if I could get it changed to an email instead of a phone call. I then blocked the email.
I don't want to get back into that cycle of irritation.