Tony (I couldn't find his last name) has written a tutorial about writing tile-based games in Flash: Tile Based Games. It is a good introduction, with breezy (if slightly fractured) explanations of the code, taken in small steps, with playable demonstrations as you move along. My son finally understands arrays, I learned something about ActionScript's object model, everyone wins.

He also has a selection of his games for when you need a break from coding!