Best international GSM card for russian holidays

[Effendi]

I moved the discussion here, since you are interested in an international card.
In my opinion Travelsim is the best solution, it's reliable and cheap. Otherwise I'd go with a Russian prepaid simcard, but international calls are usually quite expensive. Surely there are some callback services to make them much cheaper, but I wait for the help of our Russian friends.... Asick, where are you?