Before my son start cc, i do keep nice tags/tissue box/broucher to scrapbooking.
Now, ds cc every term got 1-2 projects (tiring leh..) thus will use, A4 box/tissue box/polyforms/carton box/old/mag/yakult container etc.. for his project.
Besides that, i collect the A4 paper wrapper to wrap & post my sprees items.
hmm...i also every use toilet paper roll covered with transparent color papers for my ds to play. He is hapi to see diff color of everything when play with it.
some other small items like buttons on old clothes are also kept for future use or ds projects & scrapbooking.
Another very common in my house, old t-shirts/towers are used as floormate in kitchen or spring cleaning (used & then throw).
I used to keep the water from washing machine for 3-4 round rinse for wash toilet or toilet use. But, now seldom becoz always miss it... But, will also keep the water for handwash clothes for toilet use or mop the kitchen.