The Orthodox Church had official doctrine, to which the whole Orthodox Community subscribes. Any official orthodox site is as good as any other, but remember some people write better than others, so naturally some sites will give you a better idea than others.
I like the Russian Catechism written by a very young and extremely talented bishop, Hilarion Alfeyev. But that's my preference.
I often use the official Greek Archidiocese of North America (GOARCH) site which is more than catechism. Occaisonally I also use the Serbian Orthodx site, but that is not in English.
Rarely, I will consult Orthodoxinfo.com, a very conservative source.
No, there is no one official Catechism of the Orthodox Church, but there is official Orthodox doctrine expressed by all Churches in communion with the Ecumenical Patriarch of Constantinople.
OK, thanks for the clarification and the links.