Inclusivism

Inclusivism represents one approach towards the status of other religions and their followers.

From a Christian perspective, broadly speaking, inclusivism holds that different religions may possess different degrees of revelation and that each person is responsible for what they did with whatever amount of revelation was available to them. On this view, the atonement of Christ covers all people, and can save those who are seeking God, even in the context of another religion.

It differs from pluralism in the sense that the saving work of Jesus Christ is seen as necessary for all people, making Christianity in some sense a more privileged revelation than other religions (or non-religious perspectives).

A few prominent Christians who have identified with this position or expressed ideas consistent with inclusivism (this is by no means exhaustive of all who hold to this position):

Justin Martyr
C.S. Lewis
Clark Pinnock
Dallas Willard (he calls his position "Christian pluralism" but it is actually an inclusivist and not pluralist perspective)

Also, inclusivist ideas are officially endorsed by some Christian traditions, most prominent being the Roman Catholic Church.

See also:
Wikipedia entry on inclusivism (section on Christianity)
"Salvation Outside the Church - But Why then Evangelize? : Reflections from a Roman Catholic Perspective"