I can tell that you can't even define whether a person speaking Russian is from Ukraine, Belarus or Russia, let alone parts of Russia, Ukraine, Belarus etc, if you talking about accent of urban residents. Because people who are more or less educated speak the same. But if you go to some old village people lived there all life then there's a big differences how they talk and how urban citizens talk. Also there are certain differences between some words and slang used. Once I was in Russia(I'm from Russian-speaking region of Ukraine) and my cousin used words which I hadn't heard before, and some words which I used was unfamiliar to him. So for the conclusion I'd say that there are differences between different classes of people, like poor or alcoholics would cuss a lot, village people(mostly old) would speak totally in a different manner, but within average cities there are no(or almost) difference. Or you can define it by some words probably, though it is not very useful.

it is often possible to tell what region of the country a person is from. Though dialectal difference in not in the least as formidable as e.g. in UK, and people are always understood, usually there is some difference indeed (no matter whether you are from a village or a big city IMHO). But class difference within the language is much greater than dialectal, but not because of the accent, but rather because of lexicon. Concerning villages... maybe there is sense in saying that difference is higher. Maybe. But in many cases due to degradation of small settlements.

There are also certain phonetical characteristics, different from what is accepted as 'the norm'. In the northern regions, for instance, people pronounce "o" in the unstressed position in a word as "o" (standard pronunciation of this vowel when not under the stress is more like "a" or "shwa"). In the southern regions, for instance, people pronounce the sound "g" ( г) more like "h". It's just a couple of examples that jumped on my mind, but there's lots of research in the area. As Themax has mentioned, the further people live from urban areas the more distinct their dialect is. In cities people tend to speak a more standartised language.

My grandma lives in Voronezh region, in the country, it's in the south of our country. I'm here in Moscow. I must say her Russian is rather different. Besides the pronounciation ([o] without [a] like in Moscow, for example "хОрОшО" вместо "хАрАшО" etc.) there are some special words for the things. Sometimes I even have to ask her about their meaning.))) Of course, in common we understand each other, but there ARE dialects and there have always been differences between the North and the South of our admirable country!))) I'll be glad if I could help you.)))

According to the 2002 census in Russia representatives of more than 180 ethnic groups: Russian 79.8%, Tatars 3,8%, Ukrainians 2.0%, Bashkir 1.2%, Chuvash 1.1%, Chechens 0,9% , Armenians 0.8%, other 10,4%. The peoples of Russia has more than 100 languages and dialects belonging to the Indo-European, Uralic and Altaic language families, Caucasian and Paleosiberian linguistic groups. Among the most common spoken languages are distinguished Russian, Ukrainian, Belarusian, Armenian, Ossetian, and German (Indo-European language family), Tatar, Bashkir and Chuvash (Altaic language family), Udmurt, Mari and Erzya (Uralic language family), Chechen, Avar and Darghin (Nakh-Dagestani language family), Kabardian (Northwest Caucasian language family). Russian is the native language for about 130 million Russian citizens (92% of the population of Russia). But as a rule (especially in big cities of Russia), all speak in Russian. To understand that a man from another region, you can: externally (if different nationality), the manner of conduct and, most importantly, by his accent, and even on his name/surname.