Museum of the History of Psychological Instrumentation: http://www.chss.montclair.edu/psychology/museum/museum.html

U. Toronto has an on-line "museum" of old psychological equipment: http://www.psych.utoronto.ca/museum/

University of Akron houses the Archives of the History of American Psychology (AHAP).  This is a very comprehensive site with searchable indices (and even includes products you can purchase, such as posters, films, images, etc.): 
http://www3.uakron.edu/ahap/news/news.phtml

Andrew Roberts provides an extraordinary timeline of the history of mental health: http://www.mdx.ac.uk/www/study/mhhtim.htm

the online version of APA's Historical Database.  "The American Psychological Association Historical Database is a collection of dates and brief descriptions of over 3100 events in the history of psychology": http://www.cwu.edu/~warren/today.html

APA's archives link provides lists of resources available (including images and oral histories) along with additional links.  Most of the materials listed here would need to be obtained through the APA Archives and Library (contact information provided on the site):
http://www.apa.org/archives/

"Classics in the History of Psychology": http://psychclassics.yorku.ca/index.htm