PhotoAnim is a free tool which allows 2D images to be converted to 3D animations, then shared with others.
This process can be surprisingly simple. After creating a new project, we clicked File > Import to import a PNG graphic of a cartoon fish, Animation > Initialize > 3D from Front Image View, and after a few seconds our object was converted to 3D and displayed in a preview window. Check "Symmetry" and the fish was ready for use elsewhere.
You're not restricted to working with cartoons or individual objects. It's also possible to take a photograph and animate that, perhaps panning around in a cityscape to give a sense of depth.
There are powerful and professional tools to morph or warp images, even create skeletal animations on multiple regions within a picture.
You're able to customise your work by editing or correcting images, extracting subjects from the background, maybe importing 3D objects in .OBJ or .3DS formats.
Once you've finished then you can also export your work as 3D objects, maybe videos, or even share them online at http://3dthis.com (check out that site for some great examples of what the program can do).
Version 2.11 fixes "publishing PhotoAnim animations/videos to 3Dthis.com"