Amazing set of photos of NYPD 1978-81 by Jill Freeman here:

http://www.higherpictures.com/Exhibition.aspx?c=44

RED SQUAD is a 1972 documentary, made under the auspices of Martin Scorsese's NYU production class, that seeks to document the police surveillance of protest and activist groups.

http://www.psfp.com/redrevisited.htm

Short piece on John Conn's photographs of NYC subway from early 1980s in Daily Beast:
http://www.thedailybeast.com/galleries/2009/06/10/john-conn-s-new-york-subway-photos.html

See also: Bruce Davidson, Martha Cooper, Jamel Shabazz

Bloomberg on possibility of New York reverting to 1970s New York: 

When discussing the current crisis, Mayor Michael Bloomberg, now seeking a third term, promises that he will not allow the city to return to the darkness of those days, although he stresses that it faces "giant financial problems."

"I know some are concerned that city services will erode," he recently told reporters. "Let me remind you that the city went down that road in the 1970s ... I can just tell you that we are not going to make that mistake again."