Oh- sheets for tablecloths and curtains. I buy them at thrift shops. I also buy old flannel receiving blankets at thrift shops and cut and hemmed them and used them for cloth diapers, diaper wipes, wash cloths, and, um, feminine hygiene products.
Likewise old towels that get holes in them and don't work as towels anymore. Snip the corner of old envelopes for bookmarks (you slide it over the page)
Old pallets for framing our compost piles.
I've also used a metal head board to a kid's bed for a pot rack, and taken the side rails from a toddler bed and used it to hang vintage linens for display. A ladder from a bunk bed is hanging horizontally in my sunroom with pots for plants on it. No plants yet.