National Geographic
National Geographic: Conflict on the Danube
Lesson in which students use maps and text to explore physical and cultural boundaries and the disputes over control of them. Includes two activities with comprehensive and adaptable materials.
Other
Ohio Wesleyan University: World Political Boundaries
This site has a photograph of a detailed, colorful map of political boundaries around the world with a zoom feature for a closer look. A brief description of how economic boundaries relate to political ones.