Below are some resources divided by security topics:
Vortex—Binary exploitation wargame.
Murmus CTF—YouTube live streams of binary challenges and techniques.
microcorruption—Embedded security CTF.
pwntools—A Python library built for CTFs.
GDB—The GNU Debugger.
PEDA—Extensions for GDB that assists with exploit development and reverse engineering.
Binary Ninja—Easy to use disassembler.
radare2—Debugger/Disassembler. Powerful, but it has a steep learning curve.
angr—Symbolic/concolic execution framework. Dynamic analysis tool
Web Application Security
OWASP Top 10—The Ten Most Critical Web Application Security Risks.
HackThisSite.org—Web focused challenges.
Live SQL Injection Trainer—Easily practice basic SQL injection.
WebGoat—Web application with many flaws that you can practice on.
Burp Suite—A graphical tool for testing Web application security.
Postman—A browser plugin to analyze/construct web requests
EditThisCookie—View and edit web cookies
Nessus—A vulnerability scanner.
13Cubed—This channel covers information security-related topics including Digital Forensics and Incident Response (DFIR) and Penetration Testing.
Wireshark—Network protocol analyzer
binwalk—Binary analysis tool
Veles—Binary data visualizer
NetworkMiner—Network forensics analysis tool