Ingredients: Making your own homemade soda

So, I recently had a comment on a post requesting tips for someone new to home brewing root beer. This got me to thinking-there aren't too many easily found resources giving you information on levels of ingredients to  add to your brews. There are quite a few recipes out there-but they don't explain why certain ingredients are there most of the time, and they definitely don't go into detail as to what levels of certain ingredients you need to use when trying to come up with your own sodas.
I thought I would make a list, and will add to it and modify over time as I do more and more experimenting over time.
Here we go.

Root Beer
Sassafras- 1 oz./ gallon(about 1 tbsp. if just used for a little flavor/color). There are about 3 tbsp. of chopped, dried sassafras root in every ounce, so every gallon batch is going to be about 3 tbsp. I learned the hard way that you'll still get a good flavor, but it'll be far too strong to be continually enjoyable. Too much sassafras results in a cloudy-feeling, over-steeped tea kind of bitterness in the final batch.
Sassafras is the traditional main component to old-fashioned root beers. It imparts a pleasant, familiar taste; it has a good aroma; and it imparts an appetizing and quite beautiful reddish-gold color to the brew. When you think of what root beer tastes like, you're generally picturing sassafras(or, rather, it's artificial facsimile).
Examples: Dad's Old Fashion Root Beer, A&W, Stewart's, Barq's.

Wintergreen- 1 tbsp./gallon(as a main ingredient)(1 tsp. when used as a component). Wintergreen leaves are an odd thing. When you smell them, crush them up, and put them in the brew, they taste nothing like you'd expect. Most of you know wintergreen's signature flavor profile through either Wint-O-Green Lifesavers, Winterfresh gum, or Pepsodent toothpaste. Wait...toothpaste? Yes, toothpaste. I know it seems weird to include an ingredient in your homemade soda that tastes like toothpaste, but there is one specific major-label root beer that utilizes wintergreen's savory goodness-Mug. If you're not a fan of Mug root beer, you shouldn't worry too much about including it.
Examples: Mug(with a bit of cinnamon too)

Sarsaparilla- Same as Sassafras. Sarsaparilla has an entirely different flavor profile. It's bitter but slightly sweet. I would actually put this in the same category as having the same levels of each as raw vanilla-sweet aroma, bitter taste. It is excellent when combined with other things, but is definitely an acquired taste compared to Sassafras and Wintergreen.
Sarsaparilla is almost always specifically called "Sarsaparilla", and as of yet I can't think of any major-brands of root beer that include it as part of a regular root beer's ingredients.

Orange oil, Cinnamon, Vanilla, and clove
I haven't really experimented with cloves or orange oil as of yet, but most root beers that aren't majorly influenced by any of the previous three are usually some variant level of each of these. A lot of store brands use this weird amalgam(sometimes with wintergreen included), and I equate these root beers as having a very earthy, almost dirty taste. I will talk more about
Examples: Big K, Shasta, Faygo

Licorice Root- 2-4 tbsp. for a licorice root beer, 1-3 tsp. as a component. Licorice root is probably not what you're thinking. It's more of a bitter, aromatically sweet tea flavor. Anise provides the flavor most people associate with "licorice"(such as black jelly beans). However, Licorice root is the primary flavoring component of Virgil's, and a small hint can be detected in Barq's.
Example: Virgil's Root Beer.

The rest
You can really make soda out of anything if you try hard enough, but the following is a list of common(and a few not so common ingredients), and the amounts needed to attain the flavor you are looking for.

Vanilla- 12-16 inches(usually 2 beans) vanilla bean/gallon(cream soda); 3-6 in. vanilla bean/gallon(to add a "creamy" sweet finish to other brews. Note, when you are working with vanilla bean, you must cut or split the vanilla bean open and expose the inner part of the plant to actually get any flavor out of it. The longer you steep the bean, the more vanilla is going to come through. I like a nice bite to my cream soda, so I use 2 whole vanilla beans for that purpose. With root beers and anything else I decide to make I only add a little bit.
Example: A&W sparkling vanilla(with 12-16 inches of bean), Thomas Kemper's(with about 8-12 inches and a little bit of honey). Store brands and other cream sodas use varying amounts of extract-which gives an entirely different flavor profile. It's a bit closer to white vanilla ice cream, whereas the vanilla bean is a little closer to the rich, almost buttery cream you get from a french vanilla. I prefer the bean, but extract will work in a pinch-1-3 tsp./gallon should do just fine for those purposes.

Cinnamon- 3-4 inch stick/gallon. This is even a bit too much for a standalone batch, but cinnamon is a great way to enhance a variety of things-from root beer to cola.  Actually, the generic cola flavor we are all too familiar with comes from combining cinnamon and vanilla. Note that cinnamon interacts with yeast in a very weird way when it doesn't have other things to offset the bite.
Example- Mug is a very cinnamon heavy root beer.

Raisins- These give a nice fruity kick to whatever it is that you're making, and also are invaluable for bringing clarity to your brew. 1/4 cup per gallon gives a very strong fruity flavor, but I've found for clarity and a little kick you wanna use about 4-8 raisins(chopped) per gallon.

Dried Cranberries- Same as raisins, but it gives a different kick.

Nutmeg- spicy, aromatic, complex. Slice a  small sliver from a whole nutmeg or use 1/8tsp. of ground nutmeg per gallon batch and you get a bit of a spicy kick. Great for Root Beer and colas.

Anise- This is the real source of the black jellybean flavor people picture when they hear "licorice" It's also the source of Barq's bite. I love anise, but haven't got to work with star anise yet-but I will be soon. I can, however, tell you that 1 tbsp. of crushed anise seed will give your drink a bit of it's signature flavor and the same bite you'd get in Barq's or Virgil's.

Cardamom- Aromatic and sweet cousin to ginger itself. I have brewed two batches using cardamom and I've learned the hard way that you don't need very much to get it's flavor in your drink. I made a batch with 20 pods, and that was far too spicy. I also made a batch of sarsaparilla containing 3 seed pods, and it was delectable. 3 seed pods/gallon is more then enough, but 1 or 2 for a little spice and up to 5 or 6 if you're a particularly big fan of spicy sodas(like Dr. Pepper or Ginger Brews). This works to flavor cream sodas, colas, ginger ales, and would probably add a nice touch to root beers as well.

Fruit Juices. Fruit juices can give some great flavors and provide a nice bit of acid to your brew. Really the amounts you use are going to vary on what you're looking to make. Do you want a juice-based soda? Minimum is a quart, all the way up to just throwing any extra sugar and spices into a gallon of the juice.
Are you working with lemon and lime juices? 2/3 of a cup for either or both will work just fine. Much more then that and you're looking at incredibly long carbonation times-the acidity level will slow the yeast's progress.

Dried fruits-1/4 cup on up to 1 cup depending on your desired level of flavor from that particular fruit.

Sweeteners
Cane Sugar is the best all-around sweetener. 1.75-2 cups per gallon batch. It's subtle warm hints and overt sweetness will please most imbibers, but too much compared to the strength of the ingredients will overpower their natural flavors. This isn't as big of a problem as it would be with other sweeteners, but it can still happen.

Brown Sugar. About 1.5 cups per gallon. Thick, syrupy molasses-like flavor. Great for root beers and spiced seasonal brews.

Honey. I feel this is best used as an added bonus. It imparts it's own sweetness, flavor and mouth feel to the drink. I would say 1 tbsp. is a great addition to brews with many ingredients, but 1 tsp. should suffice in lighter-flavored brews. If you add honey to a brew, you should reduce the other sugars by an appropriate amount(1/4-1/3 cup less, depending on how much honey). Some people choose to sweeten their soda with only honey. If that happens to be the case, 1 lb. of honey for a varied batch(like root beer), or 3/4 lb. for lighter brews.

I have many more sodas planned for the coming months, and in that time I will work with more and more ingredients, and will have more things to add to this list. Until that time...