VulnHub provides materials allowing anyone to gain practical hands-on experience with digital security, computer applications and network administration tasks.
HackThisSite.org is a free, safe and legal training ground for hackers to test and expand their ethical hacking skills with challenges, CTFs, and more.
Hacker101 is a free class for web security. Whether you’re a programmer with an interest in bug bounties or a seasoned security professional, Hacker101 has something to teach you.