I recently planted a stevia shrub in my garden to give me a constant supply of natural sweetener. Stevia is a herb which is native to South America, so it likes warm weather and needs a nice, sheltered sunny spot. I keep mine in a pot and move it around according to the seasons. This sugar substitute is about 300 times sweeter and has no calories or glycemic impact, making it suitable for diabetics and weight watchers.
If you have a plant, simply take a leaf and drop it into your coffee or tea to get that sweet flavour. You can also buy it as a refined powder at health stores and supermarkets, where it is often mixed with other sweeteners.