If you're grilling on the back porch and need to start charcoal briquettes, you can place a dozen briquettes in a cardboard egg carton. Light the carton, and the briquettes should be sufficiently lit by the time the cardboard is completely burnt away.
Crafting blog Sew Many Ways shares this tip and warns that you shouldn't try this with a polystyrene egg carton as you will not achieve the desired results. Just place the cardboard tray in your grill, fire pit or campfire site, and ignite.
Eggs-tra Special Campire Starter [Sew Many Ways]