Classic Light Meter Apps
Light reading gadgets
Selenium - batteries not required
Clockwise: Weston Master IV (accurate, serviced by Quality Light Metric), Leningrad 2 (?), Weston Master II (seems to match the IV) and Zeiss Ikophot (?)
Clockwise: Voigtlander VCII (almost as sensitive in low light as the built in meter in the M6), Gossen Luna Pro F (very sensitive) and Sekonic L-208 (not for low light)
When I like to travel light I go back to my roots and shoot Sunny 16 with this gizmo. It's just as good as (if not better than) any of the other toys above since it exercises my mind.