Much of this was known before, including the FBI's anonymous letter attempting to provoke a suicide. As others said elsewhere in this thread, documents came out during the Church Committee. I wrote this 15 years ago when I worked at Time:
The FBI's campaign to destroy Dr. Martin Luther
King began in December 1963, soon after the
famous civil rights March on Washington. It
started with an extensive -- and illegal -- electronic
surveillance of King that probed into every corner
of his personal life.
Two weeks after the march, the same week King
appeared on the cover of Time magazine as "Man
of the Year," FBI agents inserted a microphone in
King's bedroom. ("They had to dig deep in the
garbage to come up with that one," FBI director J.
Edgar Hoover said of the Time cover story.) Hoover
wiretapped King's phone and fed the information to
the Defense Department and to friendly
newspapermen.
When King travelled to Europe to receive the
Nobel Peace Prize, Hoover tried to derail meetings
between King and foreign officials, including the
Pope. Hoover even sent King an anonymous
letter, using information gathered through illegal
surveillance, to encourage the depressed civil
rights leader to commit suicide.
"The actions taken against Dr. King are
indefensible. They represent a sad episode in the
dark history of covert actions directed against
law-abiding citizens by a law enforcement
agency," a Senate committee concluded in 1976.
[…]
History reveals that time and again, the FBI,
the military and other law enforcement
organizations have ignored the law and spied on
Americans illegally, without court authorization.
Government agencies have subjected hundreds of
thousands of law-abiding Americans to unjust
surveillance, illegal wiretaps and warrantless
searches. Eleanor Roosevelt, Martin Luther King
Jr., feminists, gay rights leaders and Catholic
priests were spied on. The FBI used secret files
and hidden microphones to blackmail the
Kennedy brothers, sway the Supreme Court and
influence presidential elections.
http://www.politechbot.com/p-00660.html