Here's a page with links to reviews of Kingsolver's books and articles by and about the author. There's also a link to Kingsolver herself reading a thirty-minute excerpt from The Poisonwood Bible. (Free registration required.)
While Kingsolver is better known to most people through her fiction, she started her writing career writing a celebrated nonfiction account called Holding the Line: Women in the Great Arizona Mine Strike of 1983. Read more about it here.
Interested in pursuing the story of the 1983 strike further? Besides getting a hold of Kingsolver's book, you can visit this site that revolves around the issue.
One recurrent thread in Kingsolver's writing is a deep concern for human rights. Human Rights Watch has put together a beautifully organized website that will help you research any number of relevant topics.