The best plans on how to construct an extremely effective HHO dry cell, can be found here. HHO dry cell construction is actually not that complicated, although it does require some basic materials. But still, compared to a commercially available cell, you can build your own for about 1/20th of the cost, and it will be just as effective.
What can we do with our HHO dry cell, after constructing it? Probably the most popular application for those kind of cells is in a car. You can simply attach the car battery to the dry cell, build a simple watter supply, and than effectively using the hydrogen to run your car. So, basically you can make your car to run on electricity, without using gasoline or diesel fuel. Other applications can be found also -- the mixture of hydrogen and oxygen, if combined, is extremely explosive, and burns at an extremely high temperature, so the uses are endless. Dry cells can also produce electricity from a continuous flow of hydrogen and oxygen, combining them into water, and converting the heat energy into an electric current.
So, you can see that the possibilities are endless. The plans mentioned above, include everything you need, including a detailed list of the parts needed, and which stores you can buy them at. The total cost will be anywhere from 10$ to 100$ , depending on how cheaply you want to go. HHO dry cell construction becomes easy, when you have the proper knowledge, and green power is basically the future, so go ahead and construct your own fuel cell!