Here is an interesting site comparing what people say ("pop", "soda", or "coke") to what region of the country that they live in, (US only as of the moment, sorry) The best map is this one showing a county by county statistical breakdown.
It appears that "pop" is said more in the northern states not including the northeast, "coke" is said more in the south, and "soda" is said more in California/Nevada and the northwest corner. Interesting, I thought.
I was raised in Arkansas and now live in Georgia, and everyone I know says "coke" for whatever they mean. Sprite is coke, Coca Cola is coke, Pepsi is coke (although why anyone would drink Pepsi is beyond me), Diet Coke is coke, Fanta is a good way to get a beat down.