This is possibly the simplest, quickest and most gift-able project I know of. The materials are dirt-cheap, it's versatile and can add to your personal style expression. You don't even have to restrict yourself to using the 'scrunchie' as a hair accessory; use it as wrist décor, decorate your bed posts, put it on your cat for funny pictures; you name it!
Completion Time: 15 minutes
15 cm elastic
10 cm x 40 cm fabric rectangle
needle and thread
Fold over half a centimetre on a short edge, onto the back. Stitch along line. Repeat with the other short edge.
Fold the piece in half vertically, so that it appears inside out. Sew along the edge.
Turn the tube inside out.
Thread the elastic through your fabric tube and tie a knot in it.
Place one end of the fabric inside the other to cover up the elastic.