I have a cafepress.com shop--while it's not making loads of money, it is a nice little bit of extra income each month.
It's simple to set up your own original images on their merchandise--just be sure you are well informed regarding copyright laws and such before you begin. Then just sit back and allow cafepress to handle all of the order processing, manufacturing & shipping. If you choose to invest more time and effort into the promotion and marketing of your designs, some people can & do establish shops capable of generating some pretty significant income.