The written Russian language is standardised; however, the modern spoken language is not.
There are two or three major dialects recognised in Russia: northern, middle Russian (as in between northern and southern dialects) and southern dialect. There are several subgroups in each dialect.
For example, in Moscow people use the letter ‘a’ instead of ‘o’ even if the word is written with ‘o’. For example, Moskva is pronounced as Maskva, moloko is pronounced as malako, voda as vada etc. In Nizhny Novgorod, Vladimir an other regions just north of Moscow the letter ‘o’ is used i.e.Moskva, moloko, voda.
In southern dialect the letter ‘g’ is pronounced softly.
There are other differences in pronunciation and vocabulary in different regions.
For example, сем instead of семь, голуп instead of голубь, любоф instead of любовь.
It’s not always easy to locate the region to which a particular dialect belongs to but we often can hear that the speaker is from another region. I can pick up dialects from North, South, Moscow, Russians from Ukraine, from middle Asia and possibly from Ural region.
Muscovites are very good at picking up different dialects because they often meet people visiting Moscow from all over the country.
I know you can understand some Russian. Here is more information from Wikipedia on dialects in the Russian language – http://ru.wikipedia.org/wiki/%D0%94%D0%B8%D0%B0%D0%BB%D0%B5%D0%BA%D1%82%D1%8B_%D1%80%D1%83%D1%81%D1%81%D0%BA%D0%BE%D0%B3%D0%BE_%D1%8F%D0%B7%D1%8B%D0%BA%D0%B0
And on Novgorod dialect