Photoshop is useful for creating illustrations with special edge effects. Janee Aronoff offers lots of tutorials on her site, MyJanee.com.
In her tutorial on creating a torn paper, you will not only learn how to make a torn paper effect, but you will also get some practice with some interesting techniques, including the following:
TLR Edge Effects is a collection of Photoshop actions for adding popular edge effects to your photographic images.
Adding an edge effect begins by invoking one of the "Create Framed Edge" or "Create Unframed Edge" actions from the actions menu. Use one of the "Create Framed Edge" actions to add an optional black "Frame" layer for added visual impact.