Styrofoam does not deteriorate in our land fills so it must be reused as much as possible. Crafters especially find all sorts of uses for styrofaom cups, packing materials ,and many other styrofoam pieces.
As a crafter myself, I can personally tell you any piece of foam that comes my way gets turned into something useful or just decorative.
Even the foam trays from deli's or that are used to package meats , are thoroughly cleaned and used as paint palettes, bead trays , or in other craft projects.
They can aslo be broken up and used as new packing material.
Deli trays can also be used alone in shipping books etc., just place a tray on the top and bottom of the book ,secure it with a piece of tape and place it in the box.