Make3D

The good folks of Stanford University came up with a software that converts single images to 3D versions.

From their website:

'Make3D converts your single picture into a 3-D model. It takes a two-dimensional image and creates a three-dimensional "fly around" model, giving the viewers access to the scene's depth and a range of points of view.

It uses powerful machine learning techniques (more details here), to learn the relation between small image patches and their depth and orientation. This allows it to model 3-d structures such as slopes of mountains or branches of trees.

After uploading your image, you can "fly" in the 3-D scene (requires VRML viewer or Adobe Shockwave), or watch a rendered 3-d movie (flash required).'

Official website