Sweaters are really easy to upcyle into hats, and even mittens! No hoodies! The sweaters you use can't have hoods, zippers, or pockets. Turtle necks work great! You can use fabric or knit sweaters.
To make a pompom, cut about 100 4 - 6" strings of yarn and tie it tightly in a bundle in the middle. Trim the strings to your liking.