Gross, Ronald, The Independent Scholar's Handbook, 10 Speed Press, Berkeley 1982, 1993 - an indespensible book on basics of how to find out just about anything. This book essentially teaches you how to learn anything you want to at any point in your life; how to become an expert on anything that truly fascinates you.

Vansina, Jan, Oral Tradition as History, University of Wisconsin Press, Madison 1985 - discusses the uses and abuses of oral histories in working with traditions. While its primary focus is on African oral histories, the work applies across the board to any culture with an oral tradition or oral history. The Druids were famous for the orality of their sacred materials, forbidding the writing of any sacred texts. This will help you sort through the jungle of how to interpret the potential meanings of oral histories.

Harris, Sherwood, The New York Public Library Book of How and Where to Look It Up, Prentice Hall, NY, 1991 -- this book is updated every few years, but it is a truly impressive listing of everything from reference books to special collections at libraries and universities to various online databases on an extensive array of subjects. Each section is broken down alphabetically by subject, with a description of what resources each source provides.