For the classroom,  if you collect things like toilet paper or paper towel rolls I could find them useful.  Also in the future, I would love to do an art project that is like that of Louise Nevelson.  She collected random objects and assembled them.  For example, small electronics that don't work anymore that could be disassembled.  Also small items like buttons, washers, pens that don't write, small toy parts, anything small and not heavy that could be glued down to a cardboard surface.

I would really appreciate any old t-shirts that you are not using anymore.  Kids like to wear them while painting and hopefully will keep their uniform clean.