Cat Stuff -
Toys should stimulate the cat. Toy's shouldn't just lie on the floor gathering dust. They should also stimulate the owner by encouraging him/her to play with the cat. I have found that cheap remote control toys can really wake a cat up. Buy the ones that take rechargable batteries. Also excellent is a simple length of cane with a piece of string tied at one end and a few feathers tied to the other end. Just flicking this a for a few minutes can give a cat a good workout. Also simply shining a light on a wall can keep them happy for ages. Strangely, just like small children, your cat might not be as interested in the box as the toy that came in it!
Finally cats seem to find christmas trees fascinating, strictly speaking they aren't toys, but try telling the cat!
Laser pointers are great for keeping cats active while you do basically nothing.
Ribbons on the end of a stick are also very popular with cats.