I have written a few times on the large dialect survey which gets used by journalists at times to ooh and ahh over the fact that some places say soda, some say pop, and some say coke. (I come from one of the tiny areas that still has some people who say tonic, and did so myself as a child. It comes from being the development and bottling leaders of many of the original beverages sold as medicines, or "nerve tonics," like Moxie.) It's fun when they use maps.
I went looking for the survey and the maps today, and they are no longer at the Harvard site, nor at the U Wisconsin-Milwaukee site. I found the full survey here. The maps about the sweetened carbonated beverage is here. There is a similar but different survey here (no soda question!), with nice maps. Update your bookmarks accordingly.