I think there was a message similar to this some time ago so you might search the archives. I specifically remember that there was mention of The Castle of Otranto by Horace Walpole, The Monk by Matthew Lewis, and The Mysteries of Udolpho by Anne Radcliffe.
If you have the time, you might read The Tale of Terror: A History of the Gothic Romance by Edith Birkhead. This is basically an encyclopedia and analysis of notable Gothic works. Among the works that Birkhead cited were Frankenstein and The Plague by Mary Shelley, The Vampyre, a short novel by John Polidori, Northanger Abbey, a parody of Gothic literature by Jane Austen, Melmoth the Wanderer and Caleb Thorne (I can't remember who the author of these last two books was.)
Good luck!
ProfStokes