I donated blood today; when the Red Cross folks called to tell me I was okay to give blood (the 56 day wait was over) and they needed my very special blood (okay, they didn't say that my blood is special, but I'm saying it!), the Red Cross person said this donation would put me at 8 gallons (I'm guessing that's just through the Red Cross in this state, but it might also include a few donations at the Red Cross in the last state I lived in, I suppose).
So, 8 gallons. That's a lot of blood.
It looks like I wrote about donating a couple years ago, when I had just passed the 5 gallon mark.
I still haven't gotten a wall marker, though.