Cut 2-by-6 lumber planks into pieces 1 foot long. These will make shelves capable of storing about 10 VHS tapes or 15 DVDs. For each one of these, add two more pieces as long as a cassette or DVD case; 8 inches is good.
Affix the two 8-inch boards to the foot-long board, one at each end. Glue the pieces so they are standing on the foot-long board right at each edge. Nail or screw them in place to secure them further.
Repeat the process for as many shelves as you want. Stack each shelf on top of the other, gluing each one so each foot-long board firmly stands on top of the two 8-inch pieces of the shelf below it.
Add one last foot-long board to the top of your final shelf, gluing and/or nailing it in place. You will have now completed the basic frame of a VHS/DVD storage cabinet containing multiple shelves.
Create a backing for the shelves if you want one. This can be made of cardboard, plywood or some other thin yet sturdy material. Cut it into a single piece equal to the total length and height of the shelves and then glue or nail it to the back end of the shelves.