Rockler, Ana White and Lori Wall Beds all have plans for Murphy beds available. Ana White has the plans posted for free. Lori Wall Beds has downloadable PDF plans for purchase, an instructional video for an additional price and a carpentry kit with hardware. Rockler's plans are also for purchase.
Murphy beds require special mechanisms for safety. Wallbed offers that mechanism and includes legs. Moddi Day People advertises plans that allow "do-it-yourself" types to convert furniture and parts from various retailers into a Murphy bed for under $275. Amazon offers several kits including plans and instructional DVDs for both vertical and horizontal Murphy beds.