If your class is going to study the Underground Railroad, one website you should check out is Documenting the American South (DocSouth). The University of North Carolina at Chapel Hill has put together a great collection of primary sources, including slave narratives published before 1920. To see a list of what they have available, go here. Besides the full text of books, DocSouth has great supplementary material for almost every title. On Frederick Douglass, for example, the site provides a short biography and related primary sources. While students may be familiar with Douglass or Harriet Tubman, they can find on DocSouth many new interesting stories from fugitive slaves like Solomon Northup and William Wells Brown.