Here's the address, just Map-quest it, and it should give you good directions.
600 Washington Street
Wrentham, MA 02093
Here's the Phone # if you want to give them a "ring". 1-888-881-9090
They might have a moped on the lot, then again they might not. Look around or ask some one who works there they could tell you how many mopeds that usually get donated.
P.S. I thought it was in Foxborogh, guess not though.
I think that you take the Foxborogh exit on 495 South. Thats how I got mixed up. Anyways its in Wrentham.