Make your own miniature cog train, designed by Creativity Plus Ltd. This is a very cheap experience for someone who wants to get hands on with a small project.
 
No glue required! 
Kitset has small form factor
Results in a moving product
great for kids!
 
Package dimensions: 160mm*120mm, pieces dimensions: 100mm*70mm, final product: L60mm*H45mm*W20mm