I kind of miss my detachable $40 (yup!) fisheye lens used with the old Nikon 40. It attaches itself to the end of another lens, and distorts the view.
Shot during a trip to Oxford for a wonderful wedding, the rotund shape of Radcliffe Camera lends itself nicely to the convex view from a fisheye lens.
Currently looking for a good, affordable fisheye lens for the D300.