For my son's 4th birthday, he wanted pirates.  My husband and I had recently bought a new bed and the large cardboard box was perfect for making a pirate ship.(You can also just ask furniture stores to save you a box to use.) The box was HUGE, and contained rolled up cardboard which had protected the bed's high posts, as well as some white light weight Styrofoam sheeting that protected the finish on the bed. We cut the box to form a ship almost as large as our 13' x 17' living room. (We had to move the furniture.) The rolled cardboard was used for two tall masts and the sheeting was used to form the sails. We used masking tape and strips of cardboard to make the sails spread out from the masts. We even had a "cross beam" of sturdy cardboard with a large ship's steering wheel attached to it with a nut and bolt.  It really turned. In the side of the ship we cut a door that opened and shut, and drew with markers on the ship to decorate it with portholes and an anchor.  We attached small paper flags at the top of the two masts with "SS 'child's name'" on each for our son and his younger sister.  The kids at the party were given cheap plastic gold coins, strings of pretend beads, pretend jewels and other "pirate paraphernalia", as well as treasure maps for each child. The kids played treasure hunt and sailed the ship and had a great time.  My husband also outlined a pirate ship on my son's cake for me to decorate as well. The finishing touches were color coordinated streamers and decorations. The pirate ship was basically free and all the favors can be found at Dollar Tree, Wal-Mart, or other discount stores at inexpensive prices.  The party was LOW STRESS and a great success!!!!