Use wheat straw to keep vegetable gardens neat in the summer and to insulate them against the cold in the winter (when as much as a 6-inch-deep layer is a good idea). Because it contains much fewer weed seeds, straw is a better mulch than its close relative, hay. As it breaks down, straw reduces soil's nitrogen level, so be sure to apply a nitrogen-rich fertilizer. This mulch decomposes rapidly, but is easy to obtain—you can find it at farm supply stores.
Wheat straw, from Quail Country Farms, $2.25 per bale.