A collection of sources (To translate the sites into your preferred language use google translator):
ROCOR (Russian Church Abroad) anathema of 1983 against ecumenism:
Those who attack the Church of Christ by teaching that Christ's Church is divided into so-called "branches" which differ in doctrine and way of life, or that the Church does not exist visibly, but will be formed in the future when all "branches" or sects or denominations, and even religions will be united into one body; and who do not distinguish the priesthood and mysteries of the Church from those of the heretics, but say that the baptism and eucharist of heretics is effectual for salvation; therefore, to those who knowingly have communion with these aforementioned heretics or who advocate, disseminate, or defend their new heresy of Ecumenism under the pretext of brotherly love or the supposed unification of separated Christians, Anathema!
Source: http://orthodoxinfo.com/ecumenism/ecum_anath.aspx
Various resources on the Orthodox Christian view of ecumenism:
1. General info: http://orthodoxinfo.com/ecumenism/