Gigapxl project
Some folks are really serious about resolution. Have fun reading about the Gigapxl project. A custom camera, custom-designed lens, and huge film record unbelievably detailed images, though the claims are somewhat outdated (“600 prints from a digital SLR”). Have fun with some of the Google Earth images too.
The new 21MP Canon EOS 1Ds Mark IIII should allow about 100 images to be stitched together for a gigapixel image. The Zeiss ZF 100/2 Makro-Planar would likely be an excellent lens for such an application. I think I’d be perfectly happy with something more manageable though, perhaps 100 megapixels.