A few years ago I created a Filter Forge filter called Sketch and Color. I just upgraded it with new features.
When you look at the sample images there, please click on them to see them to see full size. The small renditions don't give a good idea of the result. You can see it here: http://www.filterforge.com/forum/rea...ID=11&TID=9294
FWIW, I based the internal workings of this filter on Photoshop blending and adjustment techniques. You will recognize some of them. But doing it in Filter Forge allows me to test dozens of combinations very quickly. Also, some Filter Forge blending modes work differently than Photoshop. So it is not quite the same as using Photoshop.