http://www.heathrowe.com/tuts/sketch.asp - black/white
http://www.heathrowe.com/tuts/pencil.asp - color

These classic techniques that have been around for years were among the first of the so-called "photo-art" methods. This presentation has a lot of screen shots and has good detail = a good ones for beginners to try.

Note: In the step that calls for Gaussian Blur you can substitute Noise > Dust and Scratches or Blur > Motion Blur for slightly different results.

~Danny~