http://www.kali.org/blog/

Kali Linux blog.

http://forums.kali.org

The official Kali Linux Forum.

http://pen-testing.sans.org

SANS penetration testing resources: blogs, white papers, webcasts, cheatsheets, and links useful for penetration testing.

http://resources.infosecinstitute.com/

This contains articles on various topics in information security, such as hacking, reverse engineering, forensics, application security, and so on.

http://www.securitytube.net/

This contains various videos on information security. Out of these, the ones that are especially useful for learning are the megaprimer videos such as Metasploit framework expert, Wi-Fi security expert, exploit research, and so on.

http://www.concise-courses.com/

This provides web shows and an online course related to information security. The course may not be free.

http://opensecuritytraining.info/Training.html

This provides training material for computer security classes on any topic, which are at least one day long.

https://pentesterlab.com/bootcamp/

This provides information on how to become a pentester. The material is divided into a 15-week bootcamp session. It contains the reading list and hands-on practice.

http://www.pentesteracademy.com/

This provides online information security training. It covers several topics, such as web application pentesting, network pentesting, and so on. Some of the videos can be downloaded for free, while for others you need to become a member to access them.

http://www.pentest-standard.org

This is a new standard designed to provide both businesses and security service providers with a common language and scope for performing penetration testing.

http://www.ethicalhacker.net/

Free online magazine for security professionals.

https://community.rapid7.com/community/metasploit/blog

Metasploit blog.

http://www.offensive-security.com/metasploit-unleashed/Main_Page

This website provides free training for the Metasploit framework.

http://www.codecademy.com/learn

This website provides various tutorials for learning the programming language.

http://www.social-engineer.org/how-tos/social-engineering-toolkit-training-available-now/

Social engineering toolkit tutorial.

http://technet.microsoft.com/en-us/library/cc754340%28WS.10%29.aspx

Windows Server command-line reference.

http://www.elearnsecurity.com/

eLearnSecurity is a provider of IT security and penetration testing courses for IT professionals.

http://www.offensive-security.com/

The developer of Kali Linux and provider of information security training and certification.

https://github.com/dloss/python-pentest-tools

Python tools for penetration testing.