What should I do with an entire leftover leg from a prosciutto di parma?

Find a homeless shelter that takes donated items. Donate a couple of large can of white beans or dried beans, and maybe a bag of Kale and some soup base too for them to use for a nice dinner/lunch soup.
Not all shelters take unpackaged food. So check around.

Beata Lei! Stock certainly is the way to go, especially anything involving beans or lentils.

Give it to me?

you could also make a nice stock and use it for risotto

Thanks! Figured I'd cook a white bean soup with it. Unfortunately don't have access to a saw, and have a 1960's fridge with an "icebox freezer." Thanks for the link!

Use it as a soup bone for split pea or bean soup, or which this very simple but delicious soup
http://www.wchstv.com/gmarecipes/minestronewiths.shtml

Can you saw the bone into smaller pieces and freeze?