General sites dealing with the Myers-Briggs Type Indicator
Association for Psychological Type
Temperament Research Institute
Myers-Briggs® Personality Type on the Web
(Virtual guide to Myers-Briggs typology sites on the web. New sites and original features, updated weekly.)
www.typelogic.com

Sites that describe the INTJ temperament
http://www.teamtechnology.co.uk/mb-types/intj.htm
http://www.typelogic.com/intj.html
http://www.personalitypage.com/INTJ.html
http://www.geocities.com/lifexplore/intj.htm
http://www.onlinepsych.com/allhealth/tests/ptt/intj.htm
http://www.haleonline.com/psych/intj.htm
http://www.socionics.com/prof/intj.htm
http://www.insightsystem.com/intj.htm

INTJ forums and Mailing lists
INTJ-Open
And for those who can't handle that one:
http://www.egroups.com/group/mbti-intj
http://www.egroups.com/group/INTJs
http://www.egroups.com/group/intj-tood
http://www.egroups.com/group/intj-list
(or alternatively - http://www.techcrafters.com/intj-list/)
http://clubs.yahoo.com/clubs/intjopen

Intj Webring
http://intjring.webjump.com/

Other interesting sites
Population Distribution by MBTI type.
Department of the Interior jobs by type page.
An essay by personality author Terence Duniho, including a section of famous individuals by type.
Pat Marr's Cartoons This site has cartoons, a type test and other stuff.
Hal Dendurent Lots of humor MBTI and otherwise.