Building blocks
Sturdy but light, cinderblocks are the perfect building material for a yard project. Usually a neutral color, and easily painted, you can create any sort of design you want for a bench or table.
Painted white, with dark wooden boards stacked on top, like here in the photo, they look chic and interesting, whilst not being too oppressive if you are filling a smaller space. You can even decorate them by popping flowers in the gaps.