The theme for this year is "What Does God Require of Us?" (Cf. Micah 6:6-8).
The Vatica's website vatican.va has a wealth of ideas and suggestions for prayers and activities during this week.
Here is just one of the paragraphs from the Vatican's page of the Week of Prayer for Christian Unity:
Micah’s strong call to justice and peace is concentrated in chapters 6:1 – 7:7, part of which forms the theme of this year’s Week of Prayer for Christian Unity (WPCU). He sets justice and peace within the history of the relationship between God and humanity but insists that this history necessitates and demands a strong ethical reference. Like other prophets who lived in the period of the Israel monarchy, Micah reminds the people that God has saved them from slavery in Egypt and called them through the covenant to live in a society built on dignity, equality and justice. Thus, true faith in God is inseparable from personal holiness and the search for social justice. More than just worship, sacrifices and burnt offerings (6:7), God's salvation from slavery and daily humiliation rather demands that we should “do justice, love kindness, and walk humbly with our God” (cf. 6:8).
With all the talk of weapons and arms of varying degrees or types, the one sure weapon we have is prayer. Let us make all the possible use which we can of this unbeatable weapon