I realize there's no way to mount a Canon lens on a Nikon body and get the full focus range, but is it possible to use an adapter to get a sort of extra macro, and get decent results? I'd imagine it would be sort of like using an extension tube.
I did a quick google search and found one adapter on ebay, but I'm not sure about the quality of that.
(Specifically I'm interested in the Canon MP-E 1-5x Macro lens, for which there's no Nikon equivalent.)