"Sure, we've seen homebrew digital microscopes built out of old webcams and proper digital 'scopes with USB interfaces, but if you're really serious about your closeups, Nikon's new Fabre Photo EX system is probably calling your name. The stereoscopic microscope can be fitted to a Nikon DSLR back to capture images, with max magnification based on sensor size and crop factor -- FX backs will yield 20x zoom, while a DX back will let you keep tabs on your favorite c. elegans at 45x."
Sorry Nikonians -it's pretty much a lab table piece of kit so no MPE-65mm macro lens equivalent for you. Also what Engadget says about the crop factor changing the magnification is bogus -seems like no one gets it right. Cropping an image does not change the magnification *sigh*.