Hey all! You may or may not know, but I went to college for graphic design before I realized that that was a lot of work to put out to have it line the birdcage the next day. But I did learn a great deal. Lighting and shadows are often what I spend the most time on when manipulating a fantasy page or digital art.
I did a tutorial here on shadows -
but here is the best tutorial for light & shadows of different types that I've found!