Brady tells me that when he grows up he's going to "go to college and study how to be an inventor." I have no doubt he means this as this invention idea has stuck around for awhile with him, and I also don't doubt he could do it. But I'm biased!
Even if a kid is not necessarily heading down the engineering path I think an "invention box" like we have is a wonderful tool. For one it models recycling and reuse. Here are things that can be useful rather than just tossed out.
Beyond that, it engages their creativity in amazing ways. Figuring out how to put things together works spatial skills, problem solving skills and science/math principles. Thinking unconventionally works their imagination.
And it saves money on toys! They're bored? Send them to the invention box! Here's a picture of ours and the "metal detector" Brady made with his the other day and the "toilet paper roll bowling" game he made a few weeks ago.