Wicca and Witchcraft:

Witchcraft Today by Gerald B. Gardner
The Meaning of Witchcraft by Gerald B. Gardner
Witchcraft for Tomorrow by Doreen Valiente
ABC of Witchcraft Past & Present by Doreen Valiente

Wicca: The Old Religion in the New Millennium by Vivienne Crowley
Principles of Wicca by Vivienne Crowley
Lid Off the Cauldron by Patricia Crowther
High Priestess by Patricia Crowther
Charge of the Goddess - Doreen Valiente
Circle of Fire – Sorita D'Este
Witch Blood by Patricia Crowther
One Witches World by Patricia Crowther
What Witches Do by Stewart Farrar
The Heart of Wicca by Ellen Cannon Reed
A Witches Bible (or ‘What Witches Do and Eight Sabbat’s for Witches) – Stewart Farrar
The Witches Circle by Maria Kay Simms (Non BTW)
Magical Rites from the Crystal Well by Ed Fitch (Non BTW)
A Book of Pagan Rituals by Herman Slater (Non BTW)

Neopaganism:

The Elements of Ritual by Deborah Lipp
Witchcrafting by Phillis Currot
Spiral Dance by Starhawk
Drawing Down the Moon by Margot Adler
The Witches God by Janet and Stewart Farrar
The Witches Goddess by Janet and Stewart Farrar
Ancient Ways and Wheel of the Year by Pauline Campanelli
Coven Craft: Witchcraft for Three or More by Amber K
Ethics and the Craft by John J. Coughlin
The Truth About Witchcraft by Hanz Holzer
The Paganism Reader by Chas Clifton

Historical Reference:

The Triumph of the Moon by Ronald Hutton
The Pagan Religions of the Ancient British Isles by Ronald Hutton
Wiccan Roots: Gerald Gardner and the Modern Witchcraft Revival by Philip Heselton
Her Hidden Children: The Rise of Wicca And Paganism in America by Chas S. Clifton
The Golden Bough by Sir James Frazier
The White Goddess by Robert Graves

Magic:

Modern Magick by Donald Michael Kraig
Magick without Tears by Crowley
The Training and Work of an Initiate by Dion Fortune
Mystical Qabalah by Dion Fortune
The Witches Qabala by Ellen Cannon Reed
Summoning Forth Wiccan Gods and Goddesses by Lady Maeve Rhea

Open Source:
(Note: Though most of her theories have since been debunked, Murray's works are included for reference purposes. )

The Golden Bough by Sir James George Frazer
http://www.sacred-texts.com/pag/frazer/index.htm
The Witch-Cult in Western Europe by Margaret Alice Murray
http://www.sacred-texts.com/pag/wcwe/index.htm
Aradia; Gospel of the Witches by Charles G. Leland
http://www.sacred-texts.com/pag/aradia/index.htm
Etruscan Roman Remains in Popular Tradition by Charles Godfrey Leland
http://www.sacred-texts.com/pag/err/index.htm
Witchcraft Today (PDF) - by Gerald Gardner
http://homepage.ntlworld.com/wisewoman/WiccaWitchcraftToday.pdf
The Meaning of Witchcraft - Gerald Gardner
http://homepage.ntlworld.com/wisewoman/TheMeaningofWitchcraft.doc
High Magics Aid - A 'fictional' book by Gerald Gardner
http://homepage.ntlworld.com/wisewoman/HighMagicsAid.doc
Gerald Gardner: Witch - attributed to Jack Bracelin but actually written by Idries Shah
http://homepage.ntlworld.com/wisewoman/GeraldGardnerWitch[1].rtf
God of the Witches (PDF) - by Dr Margaret Murray
http://www.thewica.co.uk/godwitch.pdf