Scraps are great for making a new yarn. You can even use scraps from old cloth. Like old dresses, blankets, etc... Plastic bags, just about anything can be spun into new yarns.
This site has challenged me to think outside the box when it comes to what can be spun.
Check out some of the old spin Challenges. They may be over, but its really fun to try them and see what you come up with.