|Photo is from linked blog.|
"Not Dabbling in Normal" knew so I'm linking to their blog of natural soda pop recipes.
Mix your ingredients, add yeast, wait a few days for it to get fizzy, pour it over ice. Natural carbonation results from the early stages of fermentation; you simply halt the process before the concoction becomes an acoholic beverage. I believe I'll start with the ginger-ale. This may be the treat of summer 2012: Here's the blog of recipes.