Perfect Game (
http://www.perfectgame.org) held several midwest showcases just recently.
If your son is an '06, and now that it's "Indian Summer" in Michigan, you may have to go South for any exposure. If he's an '07 or later, you're in luck because there will be many more showcases in your area starting next summer. You can also find an "indoor" showcase over the winter if he's a pitcher or catcher.