I always cut up old panty-hose and tights to make hair ties! Though, I find that the legs make a better size hair tie than the waist. I just cut the legs into horizontal strips and they are ready to go.

The waist is better a better size for a full head band, which I use sometimes to keep my bangs out of my face.  I like it because it isn't as tight on my skull as elastic ones I have bought from the store.  I find that cutting wider strips helps them stay on better.