The first time I can remember using scratchboard was as a child. I believe we made our own scratchboard by coloring with crayons on heavy paper and painting a coat of india ink over the crayon. When the ink was dry, we would scratch our designs into the surface of the ink and expose the beautiful colors beneath.
In my high school art class we dabbled a little bit with scratchboard. I still have the piece I made, which is the Harley Davidson logo.
I recently came across a childrens set of scratchboard & scratch paper called "Scratch Magic", which is what I used to create the butterfly image shown at right. The set contained a sampling of several different types of scratch media, such as multicolor under a white coating, stained glass (transparent colors where scratched), sparkle under black coating, and regular white under black. I have come to find that Scratch Magic makes quite a few diffent types of scratch paper and scratchboard.
There are quite a few different types of scratch paper and scratchboard available. Below you will find a small sampling.
Links to Scratchboard Tutorials:
Thumbprints Custom Art
How To Do Scratchboard
Window to Art
Scratchboard Letter (mini tutorial)