The group velocity of light can be made amazingly slow in the right material, but often the apparatus required is rather exotic and requires significant cooling. Pengfei Wu and D V G L N Rao at the University of Massachusetts have made the remarkable discovery that light can go as slowly as 0.091 mm/s in a thin film of bacteriorhodopsin (a bacterial pigment) at room temperature.
More than that, it turns out that this speed can be optically controlled to be anything in a broad range from "snail's pace" to normal light speed, c. The process takes place at high efficiency, being effective for light levels down to microwatts. Bacteriorhodopsin is stable and inexpensive so this could lead to many interesting technologies.
Further reading
Pengfei Wu and D V G L N Rao 2005 Phys. Rev. Lett. 95 253601.