Well, I live some 30km away from Belgrade airport where Aviation Museum is located and would be happy to volunteer, but believe it or not our museum does not recognize the category of volunteers, although obviously desperately in need of help because last year they could not even mow the lawn around the museum due to lack of funds... Or so I heard.
I do visit the Museum from time to time though and would love to work there on permanent basis. I've posted a dedicated thread with photos I took during one of my visits there.
http://www.ww2aircraft.net/forum/warbird-displays/yugoslav-aeronautical-museum-belgrade-serbia-17442.html