I respect your enthusiasm to fight against these abuses however I must caution you. Call authorities in other countries is risky business. You do not get the same protection of privacy in Russia as you would here in the USA. Also, most of the time the FBI will refer u back to the center for missing and exploited children to file the case. if you still feel strongly about calling overseas than I recommend Interpol
I have worked with both for a long time and have blown the whistle on at least 2 major porn websites that have since been dismantled. Not to my personal credit but the credit goes to a combination of people who worked together to close them down.
I understand your anger but if you want to fight the good fight,
than read everything you can about how the evil pricks operate.
Learn the law inside and out so you don't waste time with reports that won't help build the case.
Gather information, User names, locations, times and dates. Also try to ascertain the age of the child. Keep a log of everything you do.
Don't go "undercover" and join a site or engage in direct interaction with the suspected distributors.
COPY all web addresses so you can forward them.
I have even go so far as to buy a program that lets me see IP addresses. Its a good program that can even see through other programs like ghost IP or web cloak.
Anyway, that is just a five minute overview, read everything and then fight the good fight.