The Russian Ruble is the official currency in Russia and its capital Moscow. Gone are the days when a taxi driver could easily accept US dollars. In Moscow all prices are stipulated in rubles. Visitors can still be surprised by the prices charged in Moscow''s restaurants, hotels and by airport taxi drivers. Moscow is after all the most expensive city in Russia and one of the most expensive cities in the world. However, things are gradually changing and prices for services used by tourists are coming in line with those of western capital cities.
The Euro and US Dollar are the most exchangeable currencies in Moscow and exchanged in every exchange office around town. Other currencies need to be exchanged in Retail Banks but it is a good idea to simply bring Euros or US Dollars with you as these are more widely accepted and more easily changed. You would probably get better exchange rates too.
Moscow has a large amount of foreign exchange offices, probably more than any other city in the world. So you could shop around for a better rate. Some of the exchange offices might keep a commission. In the center of the city there are plenty of exchange offices that open 24 hours, but sometimes the rate in the night time not as attractive. Airport foreign exchange offices also tend to charge a higher commission.Do not bring pound sterling notes issued in Scotland or Northern Ireland, as these tend to be difficult to change to Russian Rubles in Moscow.
Visa and MasterCard are accepted almost in any ATM, more rarely Visa Electron and Cirrus/Maestro whilst AmEx and Diners Club owners might have problems make cash withdrawals with these cards. There are plenty of ATMs (called BANKOMAT in Russian) in the center of the city, inside the metro stations, shopping malls, in the banks and at the airports, where you can withdraw cash with a rather low flat rate. But it is always worth checking. Major Credit Cards like Visa and Master Card are also widely accepted in the shops, in a large number of restaurants and supermarkets.