Water Sponges - a favorite, simply and easily made by cutting 3 sponges lengthwise into thirds. Stack them in mixed order, three on-top of three (makes a cube.) Then tie tightly with fishing line. It will take shape as you tie it. Wet, throw, repeat.
These are hair ties. A couple of ribbons and several beads and you're all set!
Homemade whiteboards made from cutting and drilling a large sheet of shower board (purchased at any home store.) These were decorated with vinyl pieces I had from Uppercase Living. I would suggest adding a marker with velcro.
Dog toys braided from strips of fleece. Cat toys were also made by tying smaller strips of fleece and feathers to a dowel rod using elastic string.