A new camera sensor design from Lytro captures light in such a way that the focus can be changed in post. Check out the demonstration images(!!!!!!) at its homepage, and the CEO's dissertation on how it works:

My proposed solution to the focus problem exploits the abundance of digital image sensor resolution to sample each individual ray of light that contributes to the final image. ... To record the light field inside the camera, digital light field photography uses a microlens array in front of the photosensor. Each microlens covers a small array of photosensor pixels. The microlens separates the light that strikes it into a tiny image on this array, forming a miniature picture of the incident lighting. This samples the light field inside the camera in a single photographic exposure. ... To process final photographs from the recorded light field, digital light field photography uses ray-tracing techniques. The idea is to imagine a camera conigured as desired, and trace the recorded light rays through its optics to its imaging plane. Summing the light rays in this imaginary image produces the desired photograph. This ray-tracing framework provides a general mechanism for handling the undesired non-convergence of rays that is central to the focus problem. What is required is imagining a camera in which the rays converge as desired in order to drive the final image computation.