Depending on your area, it can cost as little as one dollar per hour. If there aren't any formal doggie day-care places in your area, try to find a neighbor with a dog. This will give your dog some company and social doggie interaction. Another factor that many people forget is that dogs are highly intelligent creatures. Circling the same yard day after day does not provide much mental stimulation.
Most dogs like to feel productive.
If you can't take your dog with you to work, or on errands, then find somewhere you can take him. A basic obedience class is a wonderful way to spend quality time with your dog. You've never seen a mole in your yard, and your dog doesn't seem particularly fond of bugs. Bury bricks where they like to dig. Bury an electric underground fence where they like to dig.