Tea and coffee stains can be removed from ceramic cups with denture-cleaning tablets. Just fill the cup with warm water, and drop in a tablet. When the tablet stops fizzing, empty the cup, and if it's still stained, repeat the process. To whiten cloth napkins, linens, and even socks, fill a large pot with water, and drop in several slices of lemon. Bring to a boil, then turn off the heat. Add the linens, and let them soak for about an hour. Then launder as usual. Many bathroom cleansers are gritty; they may be effective at cleaning grout, but they can scratch tiles. Baking soda is a safe and inexpensive alternative. First, wet the grout, and apply the baking soda to the stained area with an old toothbrush. Work on a small section at a time, and then rinse clean.
Martha Stewart Living, Volume 2005 Special Issue 2005