I've never much gone in for 'concentrating on what unites us rather than what divides us'. For one thing, I can't see how tolerance and mutual understanding can be based on an unwillingness to face up to difference. The road to hell is paved with good intentions, and anyone who assumes that all religions are pretty similar really is likely to end up treading on a few cultural sensitivities. Besides which, some of us don't get to join in with this multifaith group hug, since what people of faith can agree on most easily is that they don't like unbelievers.
However, I'm increasingly coming to the conclusion that some day soon I may have to eat my words.
One of the most spiritually moving things I've read recently is a collection of extracts from the Upanishads, the Hindu philosophical and theological texts - translated from Sanskrit to English by a Spaniard, Juan Mascaro. The ideas in these texts, at least as explained by the extraordinary Mr Mascaro, go far beyond the myths and doctrines of Hinduism - they illuminate Christianity too, and perhaps point towards something primal behind all religions.
The first experience I had of Hinduism was through a copy of the Bhagavad Gita given out on the street by the Hare Krishnas (or International Society for Krsna Consciousness), with their own commentary. One thing that really struck me was the sense of trinitarianism in the commentary. There is a transcendent God, Brahman (usually described as the Godhead); an immanent spirit described as the Paramatman (roughly, I think, Universal Soul); and then there is a divine-human or avatar, Krishna, who is described as divine and as the perfect archetype of a human. The International Society for Krsna Consciousness (ISKCON) emphasises a relationship of love and service with Krishna, in the way that Christianity emphasises a relationship with Christ.
Of course, ISKCON is a 20th century religion with many adherents from western countries, so the parallels with Christianity are probably not coincidental. The learned and poetical introduction to the Upanishad collection by Mascaro - practically a spiritual scripture in itself - makes explicit connections with traditionally Western faiths. But in neither case are these interpretations completely imposed from outside.
The focus of these texts from the Upanishads is 'Brahman' (which is not to be confused with Brahma or a Brahmin. Obviously!) This is the true God of Gods - uncreated, transcendent-and-immanent, without size or number. Essentially, this is the same kind of god that Christian theologians have been trying to get their flocks to believe in for the last two millennia, but the Man with the Beard kept getting in the way. The Hindu writers seem to have done much better at beard-avoidance - perhaps because they have so many lesser gods to distract the anthropomorphising tendencies of the faithful - so much so, in fact, that they generally avoid the translation 'God' in favour of 'Godhead'.
The basic concept is that the Atman or individual human soul is identical with Brahman, and true enlightenment or freedom comes about through the realisation of one's own identity with the universe. I had always assumed that the aims of eternal life and freedom from reincarnation were opposite goals. In the latter, life is a rather pointless suffering from which we should wish to escape; in the former, our aim is to live forever in an improved version of our earthly life. On the contrary, the sections of the Upanishads which I've read so far often describe freedom from the cycle of life and death as a form of eternal life. The enlightened one becomes united with Brahman and thus goes 'beyond life and death', becoming one with the eternal. There are distinct similarities with the 'Eastern' (i.e. Greek, Eastern European and Middle Eastern) branches of Christianity, which emphasise the goal of union with God and ultimate 'deification' or participation in the divine. Again, though, Hinduism is braver in going beyond the literal. Some of the Upanishads talk of this transformation or union as taking place during life and 'in the mind', so that eternal life becomes a psychological state. Union with the divine is about realising that you're already there.
The main difference 'eastern' teachings such as Buddhism and Hinduism have from Christianity is that they see the main path to union with the divine as being a detachment from the world and particularly the overcoming of all forms of desire and yearning. Although there's a strong anti-material current in Christianity (and even more so in some of its heterodox offshoots) there's also room for passionate emotions and for social action. And I don't think any Christian writer would go so far as does the Bhagavad Gita, in which the prince is advised that it is not wrong to participate in a civil war against his own relatives, just so long as he concentrates on dedicating the action to Krishna rather than on any material outcome.
What the two approaches seem to have in common, though, is the idea that one can transcend good and evil; that the ultimate holiness is not just 'being very good' but actually being beyond good and evil. The Upanishads talk about the enlightened person going beyond Karma so that the spiritual consequences of their good and evil actions no longer touch them. In a similar way, St Paul describes the Christians as beyond the law. That doesn't mean that Christians should do bad things, but they have been freed from the penalties for sinfulness and the slavery to sin. Mankind, which learned good and evil in the Garden, has now transcended it.