The main reason for me to buy a Micro 4/3 camera was the ability to adapt older lenses. Not only interchangeable lenses, but although fixed lenses that I ripped off various cameras. Here are my Franken-lenses:
Top left: The 17mm/f11 lens from an Agfa LeBox Panoramic disposable camera, mounted into a Leica bodycap. Gaffer tape and superglue
Top middle: The 26mm/f2 lens from a Canon 110ED pocket camera, mounted into the helicoid of a Industar-61. I wound gaffer tape around the lens to get the internal diameter of the Industar.
Top right: The 27mm/f8 lens from a Pentacon K16 pocket camera. The K16
Bottom left: The lens from an Agfamatic 300 camera for 126 cassettes. I own two of them; well, owned. The mount is a provisional cardboard/gaffer tape mount on an M39 to M4/3 adapter. When finished it will be mounted into another m39 body cap.
Bottom middle: The Rollei 35 40mm/f3,5 Tessar from the last post.
Bottom right: A plastic lens from a Nippon K147 plastic camera, mounted with gaffer tape into a M4/3 body cap.