Games and Coding Challenges
Python
CheckiO (http://www.checkio.org/)
Empire of Code (https://empireofcode.com/)
Exercism (http://exercism.io/)
The Python Challenge (http://www.pythonchallenge.com/)
Project Euler (https://projecteuler.net/)
Code Combat (http://codecombat.com/)
ACM International Collegiate Programming Contest
Alternative site: ACM International Collegiate Programming Contest
Code Wars (http://www.codewars.com/)
Advent of Code (http://adventofcode.com/)
Code School: Try Python (https://www.codeschool.com/courses/try-python)
Python Koans (https://github.com/gregmalcolm/python_koans)
Tools
Learn git Branching (http://pcottle.github.io/learnGitBranching/)
Misc
PythonStdioGames (https://github.com/asweigart/pythonstdiogames)