Origami
Many people like to make their own paper. Engel describes a process shown to him by Robert J. Lang that is "a sandwich of aluminum foil and two pieces of tissue paper."  In this method, two pieces of paper are pasted to each side of the aluminum foil. Many people like origami because there is almost always paper. Copy paper, napkins, wallpaper, index cards, and even paper money can be used to make interesting and unique models.