A gardener friend told me about a curious annual that originated in South America ― an herb called Stevia rebaudiana (also "sweet leaf" and "sweet herb of Paraguay"), with intensely sweet, tender green leaves that grow on woody stems. I've noticed stevia at nurseries and in specialty produce catalogs.
To use stevia, think of it as a sweet green. Try the leaves sprinkled into fruit salads with strawberries or bush berries (blues, blacks, and raspberries), oranges, peaches, and pineapple. Or, as a pleasant surprise to go with a cup of tea, lay the leaves on open-faced sandwiches of thin white bread spread with cream cheese.
To make a pale green, sweet liquid to flavor regular or herbal tea, combine 1 tablespoon chopped stevia leaves with 1 cup water in a microwave-safe bowl. Heat in a microwave oven on full power (100%) until mixture has boiled about 1 minute. Cover and let cool. Pour liquid through a fine strainer into a jar; discard leaves. To store, cover and chill.
For suggestions on how to use stevia, read Rita DePuydt's Baking with Stevia: Recipes for the Sweet Leaf (Sun Coast Enterprises, Oak View, CA 1997; $12.95; 805/645-5309).