hackattic - No nonsense, real world programming challenges
WorksHub - Helping Software Engineers find paid work, learn and get hired through Open Source contributions. WorksHub is made up of computer scientists, machine learning experts and the best in talent acquisition.
Codewars - Achieve code mastery through challenge.
Hacker Noon - How hackers start their afternoons.
Real Dev - Real-life coding skill challenge
Indie Hackers - Connect with fellow entrepreneurs, developers, and bootstrappers who are sharing the strategies and revenue numbers behind their companies.