Sunlight fades construction paper, as anyone who's hung a piece of artwork in a window has discovered. Turn this drawback to your advantage by making sun prints that use everyday objects as stencils. Flat objects create sharp outlines, while bulky ones make blurrier impressions. Untreated, the images will fade eventually, but you can protect them with a UV-resistant spray.
Cut shapes from paper, and spread restickable glue on the back, then stick them to the construction paper. Tape the paper to a sunny window, facing out, and leave for at least a week (longer for higher contrast), then peel off cutouts. You can also lay three-dimensional objects (try rickrack, toothpicks, or buttons) flat on a piece of construction paper in a sunny place where they will not be disturbed.