I always wanted one of the Zeiss T* lenses, but that would have meant getting a Contax slr when I started out in photography. The Olympus E-510 afforded an opportunity to use these lenses well known for their quality on my digital slr. I chose the Zeiss Planar 50mm f/1.7 T* partly because the faster lens is expensive (although not too much more on a good day on ebay) and partly for the greater depth of field. I grew tired of trying to focus the f/1.4 lenses wide open at close focus (where I usually end up). The slower lenses avoid the thin depth of field and exposure variations on the E-system camera. The lens mount is for Contax and I bought a Contax to 4/3 adapter (from Fotodiox) to mount the lens on my E-510. The adapter is light and thin, well constructed and comes in a nice box for a reasonable price. It does not add too much weight to the camera.
Sample images for apertures f/1.7 through f/8 (diffraction can set in after f/8 so I did not include those).
If I get any more Zeiss manual focus lenses, I will include them here.
Note: All manual focus lenses are image stabilized when mounted to an Olympus E-510/E-520/E-3/E-30 camera body, given you have current firmware and set the focal length manually.