Tablet Weaving
Tablet Weaving (a.k.a. Card Weaving) is a form of making types of trim and ribbons, as well as sturdier items like horse reins, belts, and straps in general. In the Nordic regions, there have been tablets found that date back to 200 BC, so we can assume this is pretty ancient stuff. Check out some of my links - both for "Tablet Weaving" and "Reinactment" for more history and more detailed how tos.
Basically, tablet weaving is made from taking a set of cards, with holes near each corner (I'm currently using a set made from playing cards - cut to a square shape & punch holes with a hole punch ;> ). Run thread (anything from sewing thread to macrame cord, depending on the size of your holes) through each hole, and turn the cards a quarter turn, placing a warp after each turn.
Once I get 'em scanned, I'll put some pictures of my work up here.