My friend Gary Kessler hosts the web's best collection of information Security-related URLs: http://www.garykessler.net/library/securityurl.html

Listen to security presentations from past "Black Hat" security conferences.  Black Hat brings together government agencies and  independent security researchers and hackers: http://www.blackhat.com/html/bh-multimedia-archives-index.html

HOPE (Hackers On Planet Earth) presentations are the audio recordings from the annual HOPE conferences providing an edgy  perspectives on a wide variety of security issues and technologies:

Hope 5: http://www.the-fifth-hope.org/hoop/5hope_speakers.khtml

Hope 6: http://www.hopenumbersix.net/speakers.html

 Hacking articles and videos:  http://www.i-hacked.com/

 More Hacking Instructional Videos:

http://www.irongeek.com/i.php?page=security/hackingillustrated

http://www.irongeek.com/i.php?page=security/vids-by-others

SANS' Information Security Reading Room over 1600 original computer security white papers in 71 different categories: http://www.sans.org/reading_room/

The Open Source Security Testing Methodology Manual (OSSTMM) is a peer-reviewed methodology for performing security tests and metrics. http://www.isecom.org/osstmm/

Professional Hackers Linux Assault Kit Live CD (PHLAK) is a live Linux distro filled with tools designed for penetration testing: http://www.phlak.org/modules/mydownloads/