There are a lot of really good websites out there for mini-programming challenges and puzzles like Exercism, Hacker Rank, and Code Academy. These are really good for learning and definitely fill a need within the community. Yet, a lot of times they often fall short of challenging or diverse problems. For example, CodeAcademy is great for beginners and learning the syntax of a language but tends to fall short of difficult assignments and there's often ways to just print or return exactly what the step expects to "win."
The New Cool
I was reading a few articles a while back on Hacker News and stumbled across the Spotify developer's blog which like most highly technical companies details a little of their infrastructure and a handful of cool little technology successes that they can share with the public. The best little tidbit was the puzzle page I discovered after finishing one of their articles.
Now this something I can definitely get behind. The tech sector hiring process is flawed to say the least, so Spotify is throwing some public challenges to the masses to see what people respond with, and the cool part is the are interesting, directly relatable to their business, and they are pretty difficult. I would really like to see more companies doing this for people. It's a good way to gain some interest in their company and seeing who might be suited/come up with a really great solution.
The one downside is the restriction of language choice, but that's not really on them, it's probably on their testing tooling in the background based on the output and the (hopefully) protected environment in which they run it.
If you know any one else who does this hit me up on Twitter!