What's a good working tooth whitening toothpaste?

None for whitening: Hydrogen peroxide is the primary chemical used for whitening and although some toothpastes may have it, the concentration is not high enough and unless you want to sit there with toothpaste in your mouth for 30min to an hour it isn't going to do that much for you. Mechanical removal of debris and plaque daily should be enough. If you want to whiten more, call your dentist or get a take home kit.

None: Whitening toothpastes only have varied abrasives and additives to remove surface stain from the teeth. To my knowledge, there are no peer reviewed studies that confirm a toothpaste actually changes the intrinsic or internal color of a tooth.

None, really.: Whitening toothpastes are not effective in whitening teeth and can be damaging to the enamel or make the teeth sensitive. If you want whiter teeth, my recommendation is to talk to your dentist. He/she should have whitening systems that are safe and effective.