Talk about the ultimate thrift store! Over the last year I've been introduced to creative reuse stores. Depending on the store, the items are new or used. Some carry furniture and others cater to artists.
In the bay area there is Scrap. They carry new and used items that are aimed towards artists.
For example: several balls of yarn for $1, bolts of fabric, boxes of tempura paints, page protectors for black, portfolio books. I bought $80 worth of polymer clay (aka sculpey), a plastic binder, 2 scrap bundles of cord for $16!
In the east bay, there is the art depot. I haven't visited them yet, but I am told that teachers go there to buy supplies for their classes. It sounds like they have similar art supplies to Scrap.
Also in the east bay is Urban Ore. It's in a huge warehouse full of stuff. There's a used lumber yard, aisles of doors and used windows. I bought a 2 drawer filing cabinet for $14. There's a kitchen, tools, books, furniture, sporting goods and electronic section.
It is so easy to just buy everything because it is so cheap. My rule is to buy what I am going to use this week.
To look for a creative reuse store near you, look up "creative reuse+your city".