Stevia is my choice sweetener. I really prefer it in drinks over all the other sweeteners I've tried.
I prefer the liquid form, in the bottle with the dropper. It takes an average of two spoonfuls of sugar to sweeten a cup of coffee, were only a couple drops of stevia would suffice. Apparently it's 30-45 times sweeter. It also can be found as a green powder, and a refined white powder. I usually purchase mine at a local health food store. But you can also get it online at several different places, I like the NOW brand, nowfoods.com.
It does have a particular taste, which has kinda grown on me since I started using it. Though my Mom and sis, Abi, are dead set against it. Mom says it gives her a headache, and Abi doesn't like the taste. But I feel I need to mention, Abi also likes to drink watered down apple cider vinegar, sweetened with honey, so you can just keep that in mind. (I have a deep dislike for apple cider vinegar)