I’d like to share some sites with programming challenges, also known as programming puzzles. I find them very useful to learn a new language, much more than reading a lot of books. Actually, I usually read one book for beginners of the language and after that I go to one of the following sites and start to code. My favourite is /r/dailyprogrammer. /r/DailyProgrammer. Subreddit with three challenges every week or so (easy, intermediate and hard).