H. P. Lovecraft
Howard Phillips Lovecraft is best known for his rather strange stories which often involved people meddling with the remains of ancient civilizations and awakening monsters and other Things Man Was Not Meant To Know. He is one of the best-known of the horror writers of the early 1900's. His stories usually were set in New England (where he grew up), and dealt with a fictional mythology of elder gods and minions known collectively as the Cthulhu Mythos. Since Lovecraft's death, several writers have penned stories in the Cthulhu settings. Furthermore several movies and a Role Playing Game have been set in Lovecraft's dark little world.
Check this site out for a more in-depth view of the life and works of Lovecraft,
Reader's Guide to the Cthulhu Mythos
Miskatonic University, a fictional school which is the focus of several stories, held books containing the forbidden lore of the Cthulhu Mythos, volumes which could tear away sanity by simply reading the pages. Check out two websites for Miskatonic University here and here.
Various Cthulu links from Cthulhu.org.
Another page with Cthulhu Mythos resources.