Folklore and Mythology Resources:
(Please note that this is not a complete list.  These are merely the ones I use regularly.)

Books:

• A Dictionary of Creation Myths.
  From cosmic eggs and the Garden of Eden to the Spider Woman and the Gaia Principle, from myths of the Apocalypse and the great world religions to myths of love, re-birth, and science, this guide illuminates the phenomenon of creation in all aspects of the human experience.

• Bulfinch's Mythology. 
  A classic collection of myths and legendary lore. All major periods of mythology are covered, from Greek and Roman ages to King Arthur.

• Larousse Dictionary of World Folklore.
  Edited by Alison Jones.  Also available in hardcover.  This remarkable resource has over 1,500 entries covering everything from Johnny Appleseed to the Yeti, including some elements of mythology, urban folklore and modern superstitions.  While it's not a comprehensive resource, it's an excellent starting point for research.

• Mysterious Maya. By George Stuart.  Although out of print, one of the finest collections of information about the Maya and their myths.

• The Book of Letters: A Mystical Alef-Bait.  By Lawrence Kushner.  Isaac Bashevis Singer calls this book "A book which is in love with Jewish letters. It gives us a feeling which the Kabbalists always knew that the letters of the alphabet are not just letters but symbols of our history, of our philosophy, and of the life of the Jewish people. In this respect this book is unique."  An excellent reference for any student of Judaic folklore.

• The Dictionary of Festivals.  By J.C. Cooper.  A wonderful little book which describes the customs and ceremonies of some of the oldest civilizations, including the Babylonian, Chinese, Inca, Hindu, Sikh and Hebrew religions.

• The Power of Myth. 
  By Joseph Campbell and Bill Moyers.  This book is an excellent starting point for any study of mythology.  However, it is not source material, and should be used primarily as a jumping-off point.

Web Pages:

• Folklore and Mythology Electronic Texts.  A gigantic online collection of folklore and mythology texts, translated and edited by D.L. Ashliman of the University of Pittsburgh.  It has a separate section of Germanic myths, legends and sagas, as well as a good list of related links.

• Myths and Legends.  An online collection of folklore and mythology texts, including a small collection of early fantasy and science fiction stories.  It has links to many other related pages, as well as a search engine which will do keyword searches and return only folklore and mythology related links.

• Of Gods and Men: The A to Z of Mythology and Legend presents a well organized (and searchable) list of mythological and legendary people, places and things.  The descriptions are brief, but it's a great jumping-off point for research.

• The Encyclopedia Mythica.  An excellent online encyclopedia of mythological creatures, people and places.  It covers nearly every mythos from Aztec to Roman, and includes a section on folklore.