Here is a list of many of the items I find very useful. You probably already have most of these around the house. The rest, are easy to come by and are inexpensive.
glue, wiggly eyes, paint, scissors, permanent markers, thread, embroidery floss, fishing line, needle, toothpicks, paperclips, pipe cleaners, hot glue gun
fabric, paper, yarn, ribbon, wire, raffia, string, cardboard, jute
clothespins, spray can covers, plastic lids, glass jars, bells, egg cartons
shells, moss, seeds, pine cones, nuts, driftwood, rocks, twigs, cinnamon sticks, dried fruit and peels