This is apparently all over geek circles today, but I got it from “Miguel”:http://primates.ximian.com/~miguel/.
Researchers in Israel have developed colorization techniques that are almost freakish in their ability to produce natural-looking results using an incredibly simple-seeming marking-up of the original image.
Needless to say, “they have a web page devoted to it”:http://www.cs.huji.ac.il/~yweiss/Colorization/.