http://homepages.tesco.net/~eandcthomp/macbeth.htm
This essay that examines the witches in Macbeth in relation to contemporary views on witchcraft: “This paper considers the witchcraft episodes in Macbeth in relation to two sets of ideas: the crime of witchcraft, as it was understood in Shakespeare's England, and King James' experience of witchcraft. 

http://jesus-is-lord.com/kjdaemon.htm
This site contains Daemonologie written by King James I. It is often thought to be one of the sources for Shakespeare’s witches in Macbeth.

http://www.fullbooks.com/Elizabethan-Demonology1.html
“An Essay in Illustration of the Belief in the Existence of Devils, and the Powers Possessed By Them, as It Was Generally Held during the Period of the Reformation, and the Times Immediately Succeeding; with Special Reference to Shakspere and His Works”

http://www.nd.edu/~dharley/witchcraft/reading-texts.html
This site has background information on witches and it also has a section to help readers understand primary sources or witchcraft information. “In the case of witchcraft pamphlets, there are some especial problems which make it difficult to use them as straightforward evidence.  Several well-known and seemingly veracious pamphlets appear to be entirely fictitious, composed solely to make money.  Others are written at such a distance from the events that it is hard to give them much credence as factual accounts.”

http://www.personal.psu.edu/faculty/j/p/jpj1/witch.htm
An site with an interesting perspective on a 17^th century witchcraft case. Also contains a time-line of witchcraft laws in England.