So, ready to make your own soda? There are a few supplies you'll need, and why you'll need them. Most of these items should be pretty readily available to you in your local area, but I've provided you with links so that you may purchase those things you can't find.
1 large Stock Pot (I recommend at least an 8 qt.)-if you make gallon batches, this will give you room to stir and strain if necessary without worrying about spilling over the side. You can go bigger if you want to make larger batches, but to start off with it's a good guideline.
1 case(24x) of 12oz Amber long neck bottles. Each gallon batch you make will yield about 10 full bottles and 1 tester bottle(1 gallon=128 oz.), so you'll have enough bottles to make two separate batches. These bottles are really thick as they are intended for use in making homemade beer, so it's really unlikely you will run across exploding bottle problems. You can also use 2x 2 liter bottles that have been rinsed and sanitized beforehand for each 1 gallon batch, but if you're working with extracts they can stain the bottles and leave them with the flavor of the extract, plus you might find some of the chemicals from the bottles seeping into your brew, creating off flavors. However, these have their use if you really want to avoid exploding bottles.
1 Ladle to help fill your bottles. I recommend stainless steel over plastic to ensure proper sterilization-the last thing you want is a spoiled batch due to some unseen bacteria.
1 Funnel with Strainer for filling your bottles. The strainer will come in handy reducing the amount of unwanted material in each bottle. Remember to check and clear it after every couple of bottles.
Getting a pail with spigot, tubing and siphon(like the one from my New Toy article) make life much easier when you move into larger batches, but if you're making 1 gallon batches it's a pain in the ass because you need to lean the bucket forward to get the batch to drain through the tubing under 1 gallon. The funnel/ladle method is a little time consuming, but yields the best results for 12 oz. bottles. You can skip the ladle completely if you're just using 2 liter bottles, but you probably have a ladle in your kitchen already anyways.
1 bottle of Rainbow Soda Extracts, your preferred flavor. It's easiest to start off with an extract to give you an idea if you're going to like brewing homemade soda for yourself, and also gives you consistent results over using your own ingredients. If you're a fan of Faygo ROCK N RYE, you can mix equal parts Homebrew Cola & Homebrew Cream Soda and get a pretty good clone.
1 C&H Pure Cane White Sugar, 10 lb. Cane sugar gives the best flavor, and a 10 lb. bag is enough for roughly 10 gallons of homemade soda. More or less depending on your sweetness preference, but 2 cups(which is about 1 lb.) of sugar per gallon is a pretty standard amount. That'll yield about 38 g sugar/12 oz. bottle. Beet sugar will work as well, and you can always consider other flavoring alternatives-honey, brown sugar, molasses, agave nectar, stevia, equal, splenda, or sweet n low. Various amounts of these can be used or combined for different flavors. Start off with whatever is conveniently available though.
1 package of ale yeast. I have previously recommended use of champagne yeast, but have recently come to find out that ale yeast will usually shut itself down when the pressure inside the bottle becomes too high, as it is no longer a friendly environment for the yeast to multiply. This means there is almost no chance of exploding bottles.
1 Measuring Spoon Set. It is absolutely necessary to have 1/8 tsp. measuring spoon so that you can measure out your yeast-this is all that is required for a 1 gallon batch. It's good to have measuring spoons for a variety of reasons, but that one is a must have.
1 Pyrex 2-Cup Measuring Cup. Perfect size for measuring out your sugar. After using it for your sugar, you can also put 1/4 cup of bath-water warm(about 100 degrees) water in the bottom along with your yeast to kick start your yeast.
Gold Crown Bottle Caps or Black Bottle Caps to cap your bottles.
Bottle Capper - Red Baron for Homebrew You can also buy a Bench Bottle Capper, but it's three times as expensive and works just as well. The bench capper is a little easier to operate, but it's a small amount of convenience for the price-and not really recommended when you're first starting out.
That should cover everything you need to get started. Most of the supplies are probably already sitting around your house, and most of the supplies that aren't should be readily available at your local homebrew store.
Coming soon is an article walking you through the process of making your own first batch, if you haven't already done so.