Shout out to Martha for this classic...
Potatoes are wonderful mashed, baked, scalloped, or fried, but they have a less conventional use, too: as decorative stamps for personalized gift cards and tags. The best potato prints have a painterly quality reminiscent of impressionist art.
To make one, cut a potato (any variety will do) in half, and draw a shape onto the flesh with a pencil. Then, using a utility knife or a jackknife with a thin blade, carve around the outline of the pencil design, and cut away the background to a depth of 1/4 inch.
Mix gouache paints (available in tubes at art-supply stores) with a little water, then apply the paint directly onto the design with a brush; or dip the potato into a dish of paint as though using a stamp pad.
Press the potato onto blank cards, reapplying paint when the prints become faint. Each print will look unique and slightly irregular -- a work of art in itself.
To make a tag, punch a small hole in the corner of the card with a needle or an awl, and thread a piece of string or ribbon through.