Practice CTF List / Permanant CTF List

http://captf.com/practice-ctf/

Here's a list of some CTF practice sites and tools or CTFs that are long-running. Thanks, RSnake for starting the original that this is based on. If you have any corrections or suggestions, feel free to email ctf at the domain psifertex with a dot com tld.

Live Online Games
Recommended

Whether they're being updated, contain high quality challenges, or just have a lot of depth, these are probably where you want to spend the most time.

    http://pwnable.tw/ (a newer set of high quality pwnable challenges)
    http://pwnable.kr/ (one of the more popular recent wargamming sets of challenges)
    https://picoctf.com/ (Designed for high school students while the event is usually new every year, it's left online and has a great difficulty progression)
    https://microcorruption.com/login (one of the best interfaces, a good difficulty curve and introduction to low-level reverse engineering, specifically on an MSP430)
    http://ctflearn.com/ (a new CTF based learning platform with user-contributed challenges)
    http://reversing.kr/
    http://hax.tor.hu/
    https://w3challs.com/
    https://pwn0.com/
    https://io.netgarage.org/
    http://ringzer0team.com/
    http://www.hellboundhackers.org/
    http://www.overthewire.org/wargames/
    http://counterhack.net/Counter_Hack/Challenges.html
    http://www.hackthissite.org/
    http://vulnhub.com/
    http://ctf.komodosec.com

Others

    https://www.onlinectf.com/challenges/
    https://backdoor.sdslabs.co/
    http://smashthestack.org/wargames.html
    http://hackthecause.info/
    http://bright-shadows.net/
    http://www.mod-x.co.uk/main.php
    http://scanme.nmap.org/
    http://www.hackertest.net/
    http://net-force.nl/
    http://securityoverride.org/ Some good concepts, but "canned" vulnerabilities (string matching on input) will frustrate knowledgable hackers and teach newbies the wrong lessons

Meta

    http://www.wechall.net/sites.php (excellent list of challenge sites)
    http://ctf.forgottensec.com/wiki/ (good CTF wiki, though focused on CCDC)
    http://repo.shell-storm.org/CTF/ (great archive of CTFs)

Webapp Specific

    http://demo.testfire.net/
    http://wocares.com/xsstester.php
    http://crackme.cenzic.com/
    http://test.acunetix.com/
    http://zero.webappsecurity.com/

Forensics Specific

    http://computer-forensics.sans.org/community/challenges
    http://computer-forensics.sans.org/community/challenges
    http://forensicscontest.com/

Recruiting

    https://www.praetorian.com/challenges/pwnable/
    http://rtncyberjobs.com/
    http://0x41414141.com/

Paid Training

    http://heorot.net/

Downloadable Offline Games

    http://www.badstore.net/
    http://www.owasp.org/index.php/Category:OWASP_WebGoat_Project
    http://www.owasp.org/index.php/Owasp_SiteGenerator
    Damn Vulnerable Web App
    Stanford SecureBench
    Stanford SecureBench Micro
    http://www.irongeek.com/i.php?page=security/mutillidae-deliberately-vulnerable-php-owasp-top-10

Virtual Machines

    https://pentesterlab.com/exercises/
    http://sourceforge.net/projects/metasploitable/files/Metasploitable2/
    Damn Vulnerable Linux (not currently live? local mirror)

Inactive or Gone

Just around for historical sake, or on the off-chance they come back.

    http://rootcontest.com/
    http://intruded.net/
    https://how2hack.net
    WebMaven (Buggy Bank)
    http://www.foundstone.com/us/resources/proddesc/hacmetravel.htm
    http://www.foundstone.com/us/resources/proddesc/hacmebooks.htm
    http://www.foundstone.com/us/resources/proddesc/hacmecasino.htm
    http://www.foundstone.com/us/resources/proddesc/hacmeshipping.htm
    http://hackme.ntobjectives.com/
    http://testphp.acunetix.com/
    http://testasp.acunetix.com/Default.asp
    http://prequals.nuitduhack.com
    http://www.gat3way.eu/index.php (Russian)
    http://exploit-exercises.com/ (challenges mirrored on vulnhub)
    http://damo.clanteam.com/
    http://p6drad-teel.net/~windo/wargame/
    http://roothack.org/
    http://ha.ckers.org/challenge/
    http://ha.ckers.org/challenge2/
    http://www.dc3.mil/challenge/