If your deck or patio is partially covered, drape lengths of fabric or canvas between the joists to create shade. Space out the pieces of fabric for a more transparent look, and add lights to illuminate the space at night.
DIY Outdoor Solar Light Display : 2 fence posts + 4 solar outdoor lights + 8 extra long screws + an long scrap of treated x wood. great idea for the deck or patio! Would probably use nicer solar lights!