Extraordinary Popular Delusions and the Madness of Crowds
Charles Mackay's classic is now available on-line at the Library of Economics and Liberty.
I cannot recommend this tome too highly if you want to understand bubbles, witch-hunts, crusades, and human folly in general. In light of our current financial melt-down, this masterpiece is a must-read.
I don't think Mackay mentions it, but it has been noted elsewhere that many of the "witch" burnings were due to the Church blaming these poor wretches for the Little Ice Age. Neither bubbles nor climate hysteria are new.
S