My favorite organization is "a gift of life" - it is an Israel based organization encouraging and supporting the donation of a kidney to people who are in a critical state of their disease - without any profite to the donate, it is purely for the sake of doing good and out of altruism. They publish information about the process, explain it's importance and help with bureaucracy. This initiative is based on the fact, based on medical clinical trials, that living with one kidney is almost without risk, with minimal complications. Their story began when the head of the organization, Rabbi Heber, who was a dialysis patient himself, met a young man who's parents lost their older son in a war that urgently needed a kidney transplant - but no suitable donor was found and there wasn't any organization that could help. The young man died - and the Rabbi decided to establish the organization.
The organization already arranged dozens of transplants and saved the lives of many people.

The reason I feel so connected to this organization is that a close relative of mine donated a kidney though this organization - he did not tell any of us because he didn't want anyone to object and try to make him to change his mind. We only knew about it when he was approved for a donation and was allocated a patient that will get his kidney, needless to say I was brought to tears by his pure act of charity, when every human instinct tells you to keep yourself in the safe side and do not take the risk, no matter how small.

A link to the organization's site: https://kilya.org.il/en/