This is a list of puzzles, challenges, games, CTFs, and other entertainment via coding. It can include everything from ACM-style competitions to challenges designed to teach specific languages or programming paradigms. If you would like to see some added, please feel free to open an issue or (even better) submit a pull request on the GitHub repository.

NOTE: This list is in the public domain but I would appreciate a link back or at least a mention of where you got it if you repost it someplace.

General Resources

• CTF Time
• Pineapple challenges
• /r/programmingchallenges
• Stack Overflow list

Security

Capture the Flag

See the Trail of Bits CTF Field Guide

• Baidu CTF (in Chinese)
• Cryptogeddon
• CTF365
• Embedded Security
• ISIS Lab CTF Challenges repository
• NICCS Cyber Competitions Repository
• OverTheWire Wargames
• Hacking-Labs
• p0wnlabs
• Penetration Testing Practice Lab
• Practice CTF List
• RootMe
• SmashTheStack Wargaming
• Sphere Online Judge
• Stack Exchange list
• ThreatSPACE
• Treasure Hunt
• XSS Game
• Hack This Site

Crackmes

• Crackmes.de
• Crackmes.us
• DesrevereDD0f
• Radare examples
• Think Devise Hack
• Tuts 4 You

Other

• Bluehat Challenge
• Crack Me If You Can (password cracking)
• Matasano Crypto Challenges
• Pentester Lab
• VulnHub

Programming

Code Golf

• Anarchy Golf
• Golfscript
• Programming Puzzles & Code Golf
• Regex Golf
• Vim Golf

Contests

• Al Zimmerman's Programming Contests
• Annual Berkeley Programming Contest
• Cloudball
• Code Chef
• Codeforces
• Codewars
• Eudyptula Challenge (Linux kernel challenge)
• Google Code Jam
• HackerRank
• Hello World Open
• International Conference on Functional Programming Contest
• International Obfuscated C Code Contest
• International Olympiad in Informatics
• Internet Problem Solving Contest
• Kaggle
• Mystery Twister
• Open Directory Project - Programming Contests
• Programming Contests category on Wikipedia
• Project Euler
• TopCoder
• Tuenti Challenges
• Underhanded C Contest
• UVa Online Judge
• uHunt (complement to UVa Online Judge)

Games

• BerryBots
• CeeBot
• CheckiO
• CodeCombat
• COLOBOT
• Command Line Murders
• Corewar
• Crobots
• DroidQuest
• Glitchspace
• Grobots
• Hack 'n' Slash
• Infon Battle Arena
• Lightbot
• Kodable
• Mouse Run
• NessBots
• Regex Crossword
• Robocode
• RoboZZle
• SpaceChem
• TORCS Racing Board
• Verigames
• VIM Adventures

Employment-related challenges

• CodeEval
• Coding for Interviews
• Facebook Programming Challenge
• Leetcode
• Praetorian Tech Puzzles
• TopCoder

Language-specific

• C Puzzles
• CodingBat (Java and Python)
• Dyalog APL Competition
• Programming Praxis (Scheme)
• Prolog Problems
• Python Challenge
• Ruby Quiz
• Rubeque
• Untrusted (Javascript game)