k'nex bike

isnt brilliant just a tryout really hope you like it though :)

This is a kit, but I can't help thinking that you could do something similar with (small) boxes (and other small objects)  sandwiched between flat cardboard pieces with notched edges.

Wanimokko Some rubber bands, 33 wooden blocks and 1 wooden box. And gaps. A lot of gaps, but full of possibilities. This is zizai block, a nice toy designed by Wanimokko studio.

Pixel blocks by Janod Kubix

Janod Kubix Geometrix Blocks: great way to look at shapes differently. On the Xmas list for next year.