- ChaosVPN: http://wiki.hamburg.ccc.de/ChaosVPN
- Gh0st Networks: http://www.gh0st.net/
- Hacking Lab: https://www.hacking-lab.com/
- p0wnlabs: http://p0wnlabs.com/
- pwn0: https://pwn0.com/
- PentestIT: https://lab.pentestit.ru/
- Hack A Server: https://hackaserver.com/
- Hack Me: http://hack.me/
- Hack This: https://www.hackthis.co.uk/levels/
- Smash The Stack: http://smashthestack.org/
- Hack The Box: https://www.hackthebox.gr/
- SecAdvise: https://labs.secadvise.com/
- DarkHive: http://darkhive.net/
- Avatao: https://avatao.com/
- Root-Me: https://www.root-me.org/
- Security Conference Library: http://archive.liquidmatrix.org/
- Shell-Storm.org Repository: http://repo.shell-storm.org/CTF/
- Assembly Language Step-by-Step: Programming with Linux [ISBN-13: 978-047-04-9702-9]: http://www.amazon.com/Assembly-Language-Step-Step-Programming/dp/0470497025/
- Brute Force Vulnerability Discovery [ISBN-13: 978-032-1-44611-4]: http://www.amazon.com/Fuzzing-Brute-Force-Vulnerability-Discovery/dp/0321446119/
- Bug Hunter's Diary [ISBN-13: 978-1-59327-385-9]: http://nostarch.com/bughunter
- Hacking: The Art of Exploitation [ISBN-13: 978-159-327-144-2]: http://www.amazon.co.uk/Hacking-Art-Exploitation-Book-Package/dp/1593271441/
- Metasploit: The Penetration Tester's Guide [ISBN-13: 978-159-3-27288-3]: http://www.amazon.com/Metasploit-Penetration-Testers-David-Kennedy/dp/159327288X/
- Operating Systems Design and Implementation (3rd Edition) [ISBN-13: 978-013-142-938-3]: http://www.amazon.com/Operating-Systems-Design-Implementation-Edition/dp/0131429388/
- The Art of Exploitation (2nd Edition) [ISBN-13: 978-1-59327-144-2]: http://www.amazon.com/Hacking-Art-Exploitation-Jon-Erickson/dp/1593271441/
- The Shellcoder's Handbook [ISBN-13: 978-0-76454-468-2]: http://www.amazon.com/The-Shellcoders-Handbook-Discovering-Exploiting/dp/0764544683/
- The Web Application Hacker's Handbook (2nd Edition) [ISBN-13: 978-1-11802-647-2]: http://www.amazon.com/Web-Application-Hackers-Handbook-Exploiting/dp/1118026470/
- Bug crowd: http://bugcrowd.com/
- CTF Time: http://ctftime.org/
- CTF365: http://ctf365.com/
- Hacker Cons: http://hackercons.org
- Hat Force: https://www.hatforce.com/
- Intense School: http://www.intenseschool.com/resources/
- SECore: https://secore.info/
- We Chall: https://www.wechall.net/
- WirelessPentest: https://web.archive.org/web/20140802203941/http://www.wirelesspentest.com/
- Codec Ademy: http://www.codecademy.com/
- Learn {Python,Ruby,C,Regex,SQL,CLI} The Hard Way: http://learnpythonthehardway.org/book/
- Learn {Python,Java,C,JavaScript,PHP,Shell,C#}: http://learn-c.org/
- PHP - The Right Way.: http://www.phptherightway.com/
- Rails for Zombies: http://railsforzombies.org/
- ComputerSecurityStudent: https://www.computersecuritystudent.com/
- eLearn Security: http://www.elearnsecurity.com/
- Hacking Dojo: http://hackingdojo.com/
- MDSec: http://mdsec.net/
- Offensive Security: https://www.offensive-security.com/
- Security Tube Training: http://www.securitytube-training.com/
- The Hacker Academy: http://www.thehackeracademy.com/
- nets.ec (used to be called "Blackhat Library"): https://nets.ec/Main_Page
- Codecademy: http://www.codecademy.com/
- Corelan: https://www.corelan.be/index.php/articles/
- End Game (How to Get Started in CTF): http://www.endgame.com/
- Hacking Cisco: http://hackingcisco.blogspot.com/
- Metasploit Unleashed: http://www.offensive-security.com/metasploit-unleashed/
- N00b pentesting: https://web.archive.org/web/20120412031808/http://n00bpentesting.com/lessons
- Open Security Training: http://opensecuritytraining.info/
- Pentest Standard: http://www.pentest-standard.org/index.php/Main_Page
- Router Gods: http://www.routergods.com/
- SWEET (Secure WEb dEvelopment Teaching): http://www.csis.pace.edu/~lchen/sweet/
- SEED: Vulnerability and Attack Labs: http://www.cis.syr.edu/~wedu/seed/all_labs.html
- Security Tube: http://www.securitytube.net/