Pick up old single pane windows at salvage stores, flea markets, garage sales, etc.  With the simple addition of a simple board plank to the bottom of a window, you can score a great looking wall shelf. Cut a piece of 1x8 wood down to the same width as your window. Using a pocket hole jig, drill three or four holes (depending on the size of your shelf) on the underside of your shelf to secure to the front side of the window along the bottom edge.