Paper + video of "Real-time bidirectional path tracing via rasterization"

Available here: http://www.square-enix.com/jp/info/library/  (thanks to selfshadow)

It looks pretty damn good and the technique seems to be a very likely candidate for implementation in next-gen games because it fully exploits the rasterization hardware. One of the limitations (as mentioned in the paper) is that it doesn't work well for highly glossy and perfectly specular surfaces (sharp reflections) for which ray tracing is proposed as an alternative.