Check out Lego Factory - you can design your own Lego set, or buy interesting sets designed by others.

Check out the design of this Beijing kids bookstore.

A paintball tank! [thanks, Nick]

WMJ idea of the day: A large video production studio, which would have different modular sets, and also a glorified costume shop and collection, so kids can make really cool video productions.  The studio could be rented out for birthday parties, and there could also be an after-school production class etc. It would be like Build a Bear Workshop but for making movies.