You may already know the Reader's Guide to Periodical Literature, either in its print form or in one of its electronic incarnations. That's a very handy guide to popular periodicals — newspapers, Time, Newsweek, US News and World Report, that sort of thing. They're very useful for some things, including some English papers — interviews with living authors, for instance. But they rarely provide the sort of careful analysis of literary works that you need for an English paper.
The best index to scholarly literary publications is the MLA Bibliography, a publication of the Modern Language Association. It comes out in print every year, but far more useful is the electronic version, updated ten times a year. The electronic MLA Bibliography has an important advantage over its print counterpart: the ability to combine keywords in your search. So, for instance, you can search for “Utopia and Gulliver's Travels” or “Eliot not George.”
There are other sources, including Current Contents, though MLA is usually all you'll need for most undergraduate research.