Farsthary (one of the guys bringing us Volumetrics) and Broken have been working behind the scenes to bring Photon Mapping to Blender, something which is a very exciting prospect for the future of Blender. Both of the coders have their own versions of the photon mapper in progress, but now they are joining forces to make this a reality sooner. The coding is still in the early stages, so don't expect anything amazing yet. But its the first of many steps to bring photon mapping to Blender.
Photon mapping is an advanced type of rendering technique which in an initial render phase traces rays of light from both the camera's perspective and the light source, the two being combined in a second phase to produce an accurate render. Its not quite that simple though, so for those who want more info, a detailed explanation of Photon mapping can be found on the wiki page.
In my free free time (because in my free time I'm doing volumetrics ;) I have started the implementation of a photon mapper for blender render internal, it basically allows add support for Global Illumination and Caustics."
You can read the rest of the above blog entry here.
There's quite a lengthy discussion thread going on over at BA, with a lot of opinions and interesting views on everything related to photon mapping, including more information and answered questions from Farsthary and Broken. A few render demo pictures (made by Broken's version of the Photon Mapping renderer) are shown below.