Companies such as CafePress will do all the selling of your merchandise designs as part of their online marketplace. You simply create the designs for shirts, posters and bumper stickers and sell them to the site's 11 million users. When someone purchases an item, CafePress does all the printing and shipping work. You can create multiple design lines and never have to do anything again. At the end of each month, you get a check for a percentage of the sales.