I'm not sure about a good general tutorial, but I wrote a simple tutorial for Illustrator a little while ago that covers the Pathfinder tool and a little bit of shape manipulation:
http://www.cartographersguild.com/tu...lustrator.html

The big things to learn how to use are the Pen tool, Pathfinders, and gradients. I learned initially by tracing other illustrations with the Pen tool until I had a pretty good grasp of how it worked.