First, you might want to begin by demarcating the boundaries of your discussion. Most poetry has little to do with social reform, and many theories of poetry emphasize either the way in which oral-traditional poetry sustain cultural traditions or the way poetry should be independent of morality or other practical issues ("art for art's sake"). Many people see prose as the natural medium of calls for social reform and would argue that poetry that explicitly calls for social reform is often merely versified propaganda. Once you have dealt with that introductory issue, you might divide your presentation as follows:
Poetry that indirectly illuminates social problems. This category might include poems such as Hardy's "The Ruined Maid," Kipling's "Gunga Din," and Meynell's "Lady Poverty." You can discuss how such poems make us aware of the need for social reform without overtly proselytizing.
Explicit poems of social reform. Many twentieth and twenty-first century poems, especially from ethnic movements such as the Harlem Renaissance or counter-cultural movements such as Surrealism and the Beat movement explicitly advocate social reform or protest social injustice. In this category, you might discuss whether you consider the social reform aspects of the poem as making a positive or negative contribution to the literary effect.
Songs. Many genres of song have traditionally been used as a vehicle of social protest, such as the Greek rebetika and American rap and hiphop.