If I were writing on this topic, I think I would concentrate on the idea of inaction being a sin. As missy575 outlines, there are dramatic and imperative needs in all parts of the world which need attention. Many of them are easily fixed or cured or eliminated or saved by efforts which are ridiculously easy to do or buy. Instead, it's too easy to think "out of sight, out of mind" or figure someone else will take care of it. Most religions call for its adherents to do things which will show love to their fellow men. If that's true, we're all guilty of this sin every day. The injustice of having the means to help and then doing nothing is also a sin. Matthew 25:40 says:
Verily I say unto you, Inasmuch as ye have done it unto one of the least of these my brethren, ye have done it unto me.
Or, if you prefer, Matthew 25:45 says the inverse:
Verily I say unto you, Inasmuch as ye did it not to one of the least of these, ye did it not to me.
Either way, it's a sin for people who have--even if they don't have a superabundance--not to give.
I would say that writing about the role of religion in bringing people together is of vital importance. I think that we are in an unprecedented time. All three major religions of the West are under siege, in a matter of speaking. Terrorism launched by fundamentalist organizations have targeted the state of Israeli as well as the Jewish faith. Islam is crippled by the perception of its supposed support of terror and seeking to bring forth its own principles against social prejudice and discrimination. Catholicism is suffering through a crisis of faith in terms of assessing how the Church deals with issues and allegations of abuse and misuse of power. One issue of global justice that arises from all of these instances is how these religions can seek to become a coalescing force and work together to better the lives of its followers. In each major religious experience of the West, there are narratives and voices that need to be heard in order for healing and triumph to be present. I would say that the issue at hand would be how these religions can come together in assisting one another. How can Islam be used as a bridge to help Judaism? How can Christianity act as a force to help stop the misrepresentation of Islam? How can Judaism help to bring some level of solace to the pain caused in Catholicism? The permutations on how different modes of spiritual expression can help to alleviate political and social problems are limitless and represent one approach to solve the issues that face each religion. I think that this becomes an issue of social justice present in religious expression.
There are several global justice issues of concern right now. You have peoples in places who are under the rule of extreme dictators like in Iran and North Korea. These people deserve a voice and many human rights.
We have places in the world that deny women privileges because they are the "lesser" gender.
We have countries who like to send their opinions about how a difficult situation should be dealt with, but who fail to put their money where their mouth is while the United States swims in its own debt while maintaining commitments to give humanitarian aid and military security elsewhere.
AIDS is an epidemic that can be stopped. It has infiltrated the living conditions of so many poor countries, but once again, those of us who have so much are often less willing to help those less fortunate receive some of the much needed funds to get very cost-effective help.
Each of these can relate to religion because we have responsibilities to help those less fortunate than ourselves according to the bible. Do a topical search of "widows and orphans" in a bible resource like biblegateway.com. You will learn there are many passages to support any claim you make regarding these issues.
There are more, but the most important recent one could be about the war crime committed by Sri Lanka against Tamil Elam. Do some research you will know how the Sri Lanka went on it’s way to crush innocent civilians and how they didn’t acknowledge the UN Orders. You can also write about Taliban and it’s crime against Women.