The least expensive way to shade your patio or deck is to use materials you already have on hand, such as scrap fabric or even some window screen mesh, if your patio is covered by a pergola. If willing to spend a little more, you can purchase a shade sail or a portable canopy tent.
Make your own shade sail out of colorful fabric such as striped canvas or an outdoor-grade material so it resists fading and moisture. Shade sails are usually triangular; stitch or use no-sew seam tape to create hems, then add grommets to the three corners as a means to tie the shade up to nearby deck posts or tree branches. In a pinch, use a tall shepherd's hook plant hanger to lift one of the corners. Specialty patio stores and department stores also sell shade sails if you prefer not to make one yourself.
A patio umbrella provides a little shade and can be moved to provide shade in specific areas around the patio or deck. Use more than one patio umbrella, positioned at different places around the patio, to shade a larger space, or purchase one with an adjustable angle setting for the umbrella portion of the assembly. To find an inexpensive patio umbrella, purchase it during a sale, in a bargain outlet store or even at a yard sale.
Build a pergola over a portion of the deck using reclaimed wood or even old shutters or louvered closet doors from a charity salvage yard. Enhance the shade capabilities of an existing pergola by spanning arcs of fabric every few feet along the length of the pergola. Use flour sacks or coffee bags for a rustic look, or purchase an outdoor fabric that resists fading. Mesh window screen material, stapled to the top side of the pergola, also adds a bit of shade while still allowing some light through. Build your own movable shade panels by purchasing used picture frames or making your own basic frames, then stapling fabric or mesh screen to each frame. Position the shade frames atop the pergola in the desired location, securing them in place with bungee cords or hook-and-loop straps. Climbing vines may also be used to add shade to the pergola, but it takes time for the vines to cover the area enough to provide much shade.