cheat-seat cushions: top square and individual side panels, that are an extra 4 inches tall so they can wrap under the cushion (hem at a 45-degree angle to eliminate bulk). Add a casing and cord to tie.
DIY cushions for patio furniture. Super easy. I didn't have old cushions to cover so I used layers of cheap bed padding foam wrapped in batting. Look here for how to do boxed corners that are not covered well http://craftapple.wordpress.com/2007/09/01/sewing-tip-squarely-boxing-those-corners/
Play up patterns to add excitement to an outdoor space. More ideas for outdoor furniture: http://www.bhg.com/home-improvement/porch/outdoor-rooms/outdoor-furniture-and-fabric-ideas/?socsrc=bhgpin041413strippedpatiofurniture=9