Note: Hydrate with a Homemade Bread Humidor

Cookies, cakes, and other baked goods will quickly dehydrate. You can use ordinary, mega-mart bread to keep them fresh, or to repair slightly overdone goods that are dry and crumbly from the start.
Simply toss a slice of bread in the tupperware or ziploc with whatever it is you're trying to keep moist. The water in the bread will gradually evaporate and your baked goods will absorb it.

You can take advantage of this same principle in order to soften up clumpy brown sugar. Place a slice of bread in a closed tupperware container with the sugar and microwave it for a few seconds to steam the sugar into submission. Of course, you could do the same thing with water, or probably just by putting the sugar in the microwave by itself... but that wouldn't be awesome.