I have been using Stevia for 8-9 months. It is sold in various forms: powdered and liquid.
For great lemonade, use 3/4ths cups of squeezed lemon juice, six cups of water and a teaspoon of powdered stevia. Chill and pour over ice.
I like the Sweatleaf brand of liquid stevia. On Ebay there is a seller who sells four bottles for $39.99, with free shipping. At my local healthfood store they sell the same Sweetleaf brand for $13.99 each. The ebay seller lets you select the four flavored stevia's of your choice. I have bought from several Ebay stevia sellers; if you look under their feedback you can find Legalsea (me) and so know I used them.
I use clear liquid stevia to sweeten my homemade yogurt. I use the chocolate flavored to make chocolate milk. I use the lemon or vanilla flavored if I want flavored yogurt.
I always thought that the sugar-free vanilla instant pudding from Jello lacked flavor. However, add some vanilla stevia and it becomes great. Same for the lemon Jello pudding (with lemon stevia).
I even make a quite good fudge pie using clear liquid stevia. My recipe calls for two cups of Spenda (for the bulk, actually) then a couple of squirts of stevia.
The stevia does last a long time, so it is well worth the cost.