Polyester stuffing and feathers are the two most common filling materials for pillows. But you can recycle items found around the house by making a homemade pillow filling. The pillow's density will be determined by the type of material that's used for the stuffing. An all-fabric pillow stuffing will be heavy and dense, whereas a pillow stuffed with pieces of foam from a foam mattress pad will be light and squishy. You can use either a regular foam mattress pad or a foam mattress pad patterned as an egg-crate. If you don't have a foam mattress pad, use foam from an old couch cushion or use only fabric stuffing materials. A combination of fabric and foam will make for a moderately dense pillow.
Cut up old fabric scraps from your sewing and crafts projects. Use scissors to cut the fabric into small pieces, no larger than 1-inch in diameter. Use the small scraps that are too small for quilting or other crafts -- the scraps that would otherwise be thrown away.
Cut up old clothing items, towels and linens. Use scissors to cut them into small pieces, no larger than 1-inch in diameter.
Cut up an old foam mattress pad or an old couch cushion using scissors. Cut it into small chunks, no larger than 1/2-inch in diameter.
Place the bits of fabric and the pieces of foam from the egg crate mattress pad inside a large trash bag. Blow a bit of air into the bag and shake it to mix up the contents. Store the stuffing material inside the bag until you're ready to fill a new pillow.