There's actually a soda recipe database in the recipes section. There's not too much there, but does include both syrups and fermented versions of soda. They're really the same thing, just minor conversion. I think the main thing is that we don't have many from scratch recipes that we've really put out there. They're either too complex or too simple. ArtofDrink.com lists a lemon syrup that's: juice 8 lemons, 10oz sugar, some gum arabic and lemon oil. Basically, lemon juice and sugar. Same thing for cherry syrup, and it's easier to buy cherry concentrate, or take a can of frozen juice concentrate from the freezer section.
For example, the cherries... I'd either say, crush them and macerate them in the fridge with sugar, to extract a syrup, or pit them and put them in vodka to make a cherry extract, or add sugar to make a liquor and make that a soda. It'll probably need some lemon or lime to perk it up in either situation.
I'm playing around with rootbeer as my last one tasted more like a cream soda, and I want to add something to spice it up a bit and that had around 8 ingredients in varying quantities including sarsaparilla, liquorish root, wintergreen, chicory, black pepper, star anise, coriander.