It's time to choose a community-challenge for September 2015.

• Post your challenge as an answer to this question. Feel free to resubmit non-winning ideas from previous months.
• Vote for those answers which interest you.
• At the end-of-day on Monday, August 31st, the top-voted post will become the next challenge.

Once the challenge topic is decided, post your solution as a question on the main site and tag it with community-challenge. The challenge runs throughout September (but nothing stops you from posting an entry later on).