Now most of the time Ruby Re-Usable wants to show you recycled art that goes BEYOND egg cartons and cardboard toilet paper tubes, but those materials are ubiquitous and can be reused in creative ways:

Japanese artist Yuken Teruya creates exquisite objects out of various kinds of cardboard, including toilet paper tubes (via ecofriend)

Seattle artist Eric “Two Scoops” Moore makes whimsical figurines using toilet paper tubes and other kinds of cardboard

and Enno de Kroon from the Netherlands utilizes egg cartons as canvases for his eggcubism paintings