Tomato cage. Although they're more expensive than the conically shaped ones, straight-sided cages are easier to use. Texas Tomato Cage makes a folding model that can be stored flat ($80 for a set of six 18-inch-diameter, 4-foot-tall cages; Texas Tomato Cage, 877/983-4646).
Bean trellis. An A-frame structure of 2-by-4s allows plants such as beans to get more sun and air than they would if grown against a fence. Simply attach lengths of heavy twine to both sides for crops to climb.