Houzz.com has deck and patio designs as of 2015. Trex.com and other deck and patio manufacturer websites include galleries of ideas. This Old House also has ideas on its website.
Plans for building decks and patios are available in books such as "Black and Decker: The Complete Guide to Decks." Hundreds of free plans are available online at decks.com. Inexpensive patio designs are available at mypatiodesign.com.
Better Homes and Gardens offers a lot of advice on planning patios and decks as well as links to online planners. Lowe's and other major home improvement stores carry books that have many deck and patio designs. Bobvila.com has many do-it-yourself deck and patio ideas available for free. HGTV Home Design Software allows users to create their own custom plans.