There are some Protestants who take the position that Catholics go to hell. I do not hold to that position. I do not believe God would throw a Christian into hell over a doctrinal error.
The Catholic Church today does not teach that Protestants go to hell. However, it is interesting that this is contrary to what the Catholic Church traditionally taught. The Catholic Church used to teach that Protestants went to hell. After the Second Vatican Council, the Catholic Church became more accepting of Protestantism. Now they teach that Protestants are "separated brethren." I don't know as much about the Eastern Orthodox position on this. Can somebody who is Eastern Orthodox provide more explanation of this?
God gave us the Orthodox Church to assist us in the path to salvation. To use an analogy, heaven is like a mountaintop that everyone wants to get to. And the Orthodox Church is a guided trail with provisions for the journey. Without the trail (the Bible), the guides (fellow Christians past and present), and the provisions (the sacraments), one will be less prepared to make it to the top. The Church is the normal route.
Of course, some people who have all the resources will still fail to make use of them, choosing hell instead. And there is no rule saying those who lack the best resources cannot make it to the top. The Samaritans were wrong certain things; they worshipped in the wrong place instead of belonging to the Old Testament Church. As Christ told the Samaritan woman, "salvation is of the Jews." But this didn't stop him from telling the parable of the good Samaritan, pointing to a non-Jew as an example of a godly life.
I'm a little uncomfortable writing this because I don't want to give the impression that it doesn't matter if one joins the church or not, or the equally wrong impression that it's a simple "Orthodox=saved" formula. What About the Non-Orthodox? The Exclusive Claims of the Church by Fr. David Tillman is worth a read for those interested. And of course, Matthew 25:31-end.