GreenerGrass has created an assortment of amazing gifts, from magnets to clothespins, to pocket placemats. I like the simplicity of this sign, and the message as well.
Remade creates postcards ("Box Card Children"--what an awesome, nostalgic name) from cardboard branding. She's also got clothing, wristbands, and totes.
Cardboard cupcake by artonthemenu! A whole menu of foods ala cardboard is available. 