Here are the top 10 popular programming puzzle sites that will help test your thinking and improve your programming, problem solving, and logical thinking skills. This list was compiled by Ben Dowling of Six Revisions.
Oooh! Thank you. I have an old account on Project Euler, but I hadn't touched it in a while. I recently had a breakthrough with my old Parallax Basic Stamp Board (link goes to a newer version with USB), a precursor to the Arduino. I realized I could use its limited language to make interesting things happen in a few lines. It dawned on me that I grok coding enough now that I can guess a command or type of object, review the specifics of the syntax in the command reference, and get it to run. I'm not planning to be a professional programmer, but I really like getting physical evidence that a hypothesis works.