The best thing is that you already own the yarn for this project.

Any combination of yarns that will make a bulky-to-super-bulky weight fiber, usually 5ish strands of a worstedish weight yarn. Ideally recycled, reclaimed, or cut from a felted sweater (like the light green stuff in the picture at the beginning of this post). Fiber content is not critical. I used a mish-mash. It takes a lot though--my finished blanket weighs about 5 pounds.

I’m such a cheapskate at heart. We got it all in here: recycled cotton and wool sweaters, craptastic eyelash yarn, satin ribbons, cotton in overly-bright colors, some Caron Simply Soft that simply would not go away, a wool sweater I sliced in a spiral to spin with but never used, etc. etc.