At our Summit 2008 we had Tony Sweet as our guest instructor. He showed a technique that we now call "Layer Stack Opacity Blending".
This series of tree photos were taken with slightly vertical displacements between the shots. I think it is fair to say that these images by themselves are not really that exciting (very busy). Then he showed this image:
This looked just lovely. All the busy content is gone and the essence of the tree structure is revealed.
With his Nikon camera Tony could shoot these frames and blend them in camera to get this result. Then he showed a method that allows to get the same result in post processing. He created a layer stack with all these images and applied a formula to the opacity of these different layers. The result was astounding but the manual process way to tedious for our taste. That why we created a script (right now for free) to eliminate the manual process (script can be found here).
Here is a second example by Tony Sweet.
This time Tony rotated the camera between the shots. The flower shot is nice but we find the blended result more interesting.
We found this technique very exciting at our Summit and still think it is a great way to create images.
PS: If you think this is just digital manipulation then think twice. It mirrors multiple exposures that are as old as photography.