I recently posted about Cinemagraphs (living photographs) and have had a little more experience with them since. The Mac Cinemagraph app was on sale with a substantial discount so I picked it up and have done a couple of small ones. With my most recent attempt (at http://dougtoppin.name/cinemagraphs/ ) I made a very short video of some geese paddling across a lake. The result was so-so at best but I did learn a few things including:

you really have to have an extremely stable camera (specifically a tripod), even very subtle movement will interfere with the effect
the smaller the include mask the better, if the mask captures other unintended movemement around what want to convey it will be distracting, in the case of the case I picked some of the ripples
a longer video is better than a shorter one depending on how much movement there is, with the geese I did not get enough so they are moving too short of a distance
the file size of the animated gif is around 2mb which is larger than I expected (even with reducing the size of the image)

All in all it is an interesting thing to explore in photography but you do have to look for the right scene to capture. A few examples that I’ve seen that have turned out very well include a model with a eye blink that I think is perfect. I’m keeping my own eye out for just right scene.