This site features photo, video, and downloadable instructions from easy to hard.

Something to do with stray socks. Make some sock puppets and put on a show.

This is a link to a slideshow with some basic directions and a link to a NASA activity.

Use paper tubes to create something.

Scroll down on this Bug and Buddy webpage for some Marble Run and Maze Ideas and Links to How-to

Be sure to check out the Stuff Spinner which will help you find things to build with what you have on hand.