Or you can make a traditional, lacto-fermented ale. It will be naturally fizzy and have the complex, intriguing flavor that only fermented things can, but it's still definitely a crowd pleaser. I have a recipe for root beer here: http://food52.com/recipes/12151_classic_root_beer_float_from_scratch

To make ginger ale, on step 2, instead of using sassafras and licorice, simply use some chopped or grated ginger. Topping with ice cream is optional.

Here's another in a slightly different (but equally yummy) style:
http://food52.com/recipes/12213_a_tribute_to_woody_homemade_ginger_ale_float

Make a ginger syrup and add it to some soda water. Amanda has a recipe for it: http://food52.com/recipes/12143_gingerale_with_cucumber