While it may not be as complex as some other Rube Goldberg machines, Melvin the Mini Machine is at least portable.
Created by Eindhoven design studio HEYHEYHEY, Melvin extends across two suitcases and was built to rubber-stamp a friendly message onto a postcard and affix a postage stamp so that the postcard is ready to send. Watch as Melvin uses a bow a tie, a smoking pipe, a mouse trap, a choo choo train, and ever so tiny porcelain clogs to make the simple task necessarily complex and thoroughly amusing.
[via This is Colossal]