At more than half of the estate sales hereabouts, you will happen upon linen tablecloths. Many of them have never been used. Generally they are unbelievably cheap - always less than five dollars. They remain unsold, I think, because they are tragically yellowed. This situation is remedied by an old recipe I remember from the Hints from Heloise newspaper column. The only drawback is that it is a chemical cocktail - less than gentle to the earth. Everything is a trade-off, I guess.
White-and-bright concoction: In a non-reactive vessel (I used my plastic bathroom garbage can) pour in a large kettle of boiling water. Add the amount of powdered dishwashing detergent you would use for a load of dishes. Currently I'm using the tablet-type detergent, so I used one of the tablets. Add a half cup of chlorine bleach (did I mention you should do this in a well-ventilated area?) Add the hottest tap water you have to fill the container half full. Put your yellowed items in the water. If the cloth isn't covered by the water, add more hot water. I let this sit over night. I pour all of this into the washing machine and send it through a regular cycle with an extra rinse. I've had good luck using this recipe with baby clothes (rinse very thoroughly), men's undershirts with icky pit stains and white curtains. As I recall from the original article, nurses used this concoction to whiten their uniforms. Remember when nurses wore uniforms?