I would read code on codereview.stackexchange.com. If you're not familiar, it's a site where you can get help making your code more readable and more idiomatic.

I would read code on codereview.stackexchange.com. If you're not familiar, it's a site where you can get help making your code more readable and more idiomatic. I'd browse the questions for questions you're interested in and look at the suggestions for improvement. Personally, I don't like traditional OOP, so for me, Go and D are interesting to me (read the standard libraries if interested). Go tries to restrict you to their "idiomatic" style, and D tries to let you program in whatever style is appropriate for the problem. My best advice is to solve a real problem in a new language. Try to make that solution as idiomatic as possible for that language. Trying a functional language like Haskell or Racket will also do you a lot of good.