Dave Holt's family of wind-inflated dogs are some of the most popular "line laundry" items around.  They can be attached to the line of any kite with sufficient lift, and will entertain all who see them.  "Spot Jr." is 4ft long, so a nice size for medium-sized kites to hoist.  His brothers and sisters come in 8ft and 4ft sizes, and look great in a group.  No assembly needed, just take it out of the bag and pop it into the air.