Well, I guess the biggest most obvious difference for a foreigner would be that between the rest of Russia, and that of the southern parts (south of Rostov on don), Ukraine, and parts of south eastern Beloruss.

Other than that, to a foreigner the differences would probably be minuscule.

I've done reading on this before and apparently there are differences in accents if you travel even short distances, say, from Ryazan to Tula. Or SPB to Murmansk. But these are subtle, much to the differences that an American would be able to note between the accents in say, the state of Oregon, and in the Midwest, like Minnesota.

A Russian probably wouldn't be able to understand why people from Texas laughed at the guy from Milwaukee who said "Oh its snowing don't ya know!"

I mean, do you get what I'm saying?