Really Right Stuff, purveyors of fine camera accessories, have recently added a new product for the Leica M digital rangefinders. The BM9 is a version of their famous L-plates that allows cameras to be mounted on a tripod (using any Arca Swiss style clamp) in either the horizontal (landscape) or vertical (portrait) orientation without having to tilt the tripod head over 90o, forcing the photographer to have to completely recompose the shot and altering the center of gravity of the tripod.
The BM9 is actually much more than an L-plate. It is a system that allows for custom combinations to suit the needs of any photographer. Consisting of a Base Plate, an L-bracket, and a Grip, the BM9-B stylishly adds multiple mounting options to Leica digital M cameras while shoring up handhold-ability for folks with large mitts (like yours truly).