Digital Camera Backs
Camera backs are basically the body of the camera without the lens. Many stores sell the backs only and you can choose which lenses and accessories you'd like to add. This is a less expensive way to buy your camera if you are planning on using a different lens than the one that comes with the camera.
There are also camera backs that can transform analog SLR cameras into digital cameras. With these backs you have the choice of taking digital or analog photos from shot to shot.
A digital camera back is built to operate as a self contained unit as they are actually just sophisticated light sensing units. Digital camera backs can be attached to professional medium format SLR cameras. Digital camera backs are a good way to smooth the transition from film to digital photography.
Camera backs cost about the same as a camera.