BOOKBINDING - make a book out of loose sheets of paper (ie all the papers in those fat binders)! Can handle up to 200-400 pages.
How to Build Your Own Terrarium
Kids Garden - Make Your Own - Gardening
Take a ticket stub, plane ticket or whatever to kinkos, have them blow it up, print it on that fabric transfer material to make a pillow. This would be so fun for big trips or things done as a couple (honeymoon tix, first concert together, etc)
DIY stamped hangers
tutorial for making your own wings from cardboard, paint, and gold foil