- Causes puzzles
- Dropbox challenges
- Facebook puzzles
- Google Code Jam
- Google puzzles
- ita Software puzzles - archives
- Milo
- missing?
- Second problem - gist copy
- Quora challenges - gist copy
- Code Eval
- Coder Loop
- Codeforces
- ICPC
- NotPron
- Project Euler
- Python Challenge
- Sphere Online Judge
- Top Coder
- UVa Online Judge
- USACO
Comment or email medecau at gmail dot com so I can add more challenges to the list.