To help answer your question, let me first of all explain what economic injustice is. In a nutshell, economic injustice occurs when some people have more financial advantages than others as a result of systemic problems like racism. The pay gap is one way in which economic injustice manifests itself. An example for the pay gap is when two people do the same job, but one person earns more money than the other one, despite the fact that they are doing the exact same work. Professional sports is an example for this: there is a massive pay gap between male and female athletes.
Economic injustice can also exist between members of different ethnic or racial backgrounds. Furthermore, it can be seen in the chances in life available to rich people compared to the opportunities available to poor people.
There are several organizations which try to combat economic injustice. You could mention A Continuous Charity (ACC), a charity to tries to help young Muslims to be better integrated into society and gain access to higher education. It is a fact that many Muslims in America are in a worse financial situation compared to their white American peers. As a result, they struggle accessing good education, which leads to worse chances in getting a well-payed job. ACC tries to help overcome this gap.
Another organization you might want to investigate is the National Committee on Pay Equity (NCPE), an organization which aims at closing the pay gap between men and women, as well as between people of different racial or ethnic backgrounds.