Get the free, step-by-step plans to build your Dovetail Jig from WoodsmithPlans.com.
When I first saw this dovetail jig, I thought the advantage would be the low cost. All you need is some standard, off-the-shelf hardware, 5 board feet of hardwood, and a piece of hardboard to make your own "comb" template. However, as I looked into the project further I found some improvements over manufactured dovetail jigs, as well.
Unfortunately, too many woodworkers never try their hand at dovetails because they seem intimidating, but with this jig or a even a purchased one, for that matter, cutting professional-looking, half-blind dovetails is as easy as running your router.