Soda is easy. You can buy the soda extracts, and then mix them up with sugar and water. You add about 1/4 teaspoon of yeast, and then sanitize everything. I like to pour through a sanitized plastic funnel (making the mix up in a pitcher) and then close up.
For safety's sake, you should really use plastic bottles. I use either soda bottles, or the PET bottles designed for beer/soda. Leave them at room temperature, and when they get hard you put them in the fridge. You want to put them in the fridge when they are carbed up- otherwise the yeast keep eating the sugars and you'll have bottle bombs.
I like to make 2L or so at a time, because that's managable in my fridge. I keg, now, though, so I don't use yeast any more. I bought a carbonator cap, and force carb with it.
Broken Leg Brewery
Giving beer a leg to stand on since 2006