This linked article discusses health benefits to donating blood. Google for more.
Health Benefits of Donating Blood - Donate Blood
I also like the free stuff.
I donated for about the 54th time on July 11, 2014. That's counting lone donations in the Twin Cities and Belmont, CA. And a few donations to Life South here in the Villages area. And a few additional ones in the Tampa Bay area made after I first registered with the organization (Florida Blood Centers?) that became One Blood back around 2005 or 2006.