I save the postal envelopes that are flat- to cut templates from. I save the inside cardboard from the Joann's fat quarters for the same thing. I save squishy packaging to reuse. I save the boxes from my Ebay frenzy for building my stash and send out boxes of "stuff" to friends so they can build a stash too.
I brought home the desk calendars from last year that didn't get used. Turned over, they are blank, I can't throw away big sheets of paper. When I get over my fear, I will learn paper piecing and use these papers.
Probably more, but this is all I can think of right now.