From a cognitive development standpoint, you could argue that the strength of Lego is also its only drawback: The parts are standardized. Which is to say, a child never has to think about the connections or the materials, as they're both fixed. They are free to create--as long as they remain within the boundaries of what the building blocks are capable of.
Enter Makedo, which is something like Lego for the real world. It's a system of connectors that lets the child join a variety of material together, paper cups, cardboard, empty boxes, and whatever else you've got laying around. A series of simple (and safely blunted) tools enable the child to perform primitive construction operations and modify materials to accept the connectors, truly reinforcing the notion that you can shape the world around you with a little imagination and elbow grease.