This easy to follow PDF guide shows you how to make your own electric cigar box guitar. Its author Ed Vogel says

Before the 1950s, when factory guitars became less expensive, many folk musicians built their own stringed instruments. Wooden cigar boxes, which were solidly constructed connoisseur objects, became a popular choice for the instruments’ bodies. Thus, an American tradition was born, and today, the cigar box guitar is enjoying a folk revival. My guitar is a simple, three-stringed design that uses only one power tool and common hardware. Despite its low cost, this guitar plays real music and will hold its tuning for a couple of days. A kid can build it (and play it), and so can you.

These are the part you will need (total cost should not exceed $30): Pen, pencil, or markers (not shown) Scissors (not shown) Cigar box Mason twine,#15 and #18 ¼"x3" eyebolts andnuts (3) #12x3" wood screws (3) Drill and drill bits 3' length of 1x2 red oak ¼" square hardwoodstock, at least 1½" long ½" square hardwood stock, at least 1½" long Super glue 90-second epoxy (or 5-minute epoxy) ¼" washers (6) ¼" wing nuts (3) 2" common nails (at least 3) Phillips screwdriver 3½" x 1" (size 33) rubber bands Hacksaw blade or hacksaw OPTIONAL 1500-3000Hz piezoelectric element, a.k.a. piezo buzzer plus ¼" phono jack (with Soldering iron, solder, and wire)

Link: Makezine PDF guide to making an electric cigar-box guitar (large file - 28MB!)