InstantPhotoSketch is a free one-task utility that allows you to transform your photographs or any other images into pencil sketches or drawings in the simplest way. The conversion is immediate, and can be further customized in an easy way using the two sliders provided (one for the white areas, and another one for the black lines).
Though it can only deal with one image a time, this lack of batch support can also be seen as an advantage, as the settings that are good for one image may not always produce the same optimal results with images havong different light, contrast, or color levels. Dark images will require lighter black lines to make small details appreciated, while photographs with higher luminosity will need a much lower white level. Either way, the retouching process is certainly simple and rewarding. The program’s real-time previewing capabilities allow you to see the results as soon as you change the position of the sliders. Not all images look well as sketches, but as it is a free tool, you will not lose anything by trying.
There is also a pro version of the program with some extra color, poster, oil, and comic effects for you to apply to the resulting drawings. This commercial version comes with its own trial, which you can download separatly.