Towards the end of the nineteenth century many protestant Christians began to regret the conflict and divisions within the Church, and efforts were begun to try to re-unite churches and bring about unity between the various groups. Early efforts resulted in formation of the Evangelical Alliance (1846), an over-arching body to speak on behalf of evangelical churches, the YMCA (Young Men’s Christian Alliance, 1844), and in 1910 a World Missionary Conference was established to recognise the various missionary activities of all of the different protestant churches across the world. In 1948 the World Council of Churches was established, bringing together the majority of protestant churches with the aim of speaking as a united group to the post-war world of that time.
Alongside, and in response to the above, some churches did actually decide to amalgamate, putting aside their former differences and combining resources. The first significant example of this was the Church of South India, established in 1947 from Anglican, Methodist, Congregationalist and Presbyterian churches. A similar amalgamation was established in the north of India in 1970. Here in the UK, Congregationalist and Presbyterian churches decided to unite into the United Reformed Church in 1972, and in the USA various other churches combined to create new alliances. The Catholic and Orthodox churches have been more reluctant to participate in such alliances, considering other denominations as offshoots of the true church, who now need to return back to their original fold. More recently (1st November 2003) the Anglican and Methodist churches agreed to fully accept each other, and, although not yet ready to fully amalgamate into a single church, nevertheless have made that one of the goals of their signed Covenant
 Read the text of the Covenant here: http://www.anglican-methodist.org.uk/full-text-of-the-covenant/