Digiscoping, is simply a combination of digital photography and a spotting scope i.e, using a digital camera with a spotting scope to come up with hugely zoomed in images. In its simplest form one would just hold the lens of the camera against the eyepiece of a scope , focus and click. However digiscoping is evolving and there is now specialised equipment for connecting the camera to the scope and holding it in place. The following site will give you a better idea.
However, digiscoping is still an evolving art and the big camera/scope manufacturers are yet to come out with a single piece digiscope (Im told its already happening) so, for the time being one has to match a camera with a scope. Not all cameras will match all scopes. Usually cameras which work have a 3-4x zoom no more. Any higher and images occur vignetted - a phenomena where dark circles occor at the outer edge of the image as shown in the image below:
The Nikon coolpix series of cameras are the cameras of choice as they have just the right zoom, little vignetting and most of them have an internal zoom which means that that their lens does'nt move out of the body on zooming. This allows the camera to be placed against the scope eyepiece and eliminates fear of damage to the lens while zooming.
However, other cameras will work well too. Its a matter of trial and error to find the right match between camera and scope.
The following links will give the reader more information on Digiscoping:
I`ll leave you with a slideshow of digiscope related images. Hold your breath cause some of these images can take your breath right away