A. Yes, yes, it’s a Mitzvah! There is Halachic dispute about organ donation if one can not live without that organ (this is a complex issue that has to do with the official designation of death, brain death or cessation of breathing etc) but all rabbinic opinions agree that kidney donation (as opposed to say a heart transplant) is halachicly permissible, and giving blood is certainly permissible and highly commendable. So go ahead and schedule that blood drive!

Some things to be aware of in a Jewish community or with potential traditional Jewish blood donors: We can not give blood on Shabbat or Jewish holidays and its not a good idea to give blood on a Jewish fast day.