They can be used for sewing or be given to someone who sews. I sew a lot & reuse items from clothes:buttons, zippers, beads, portions of the fabric that are not stained. I've also used fabric for stuffing toys rather than buying the poly-fil stuff.
Then there's rags, braiding into rugs...are you crafty at all? If not, someone who is may use the clothes.
I believe clothes that are 100% cotton can be composted.