This isn't connected to a challenge, but I'm trying to understand how the badge system works, and whether it's possible to gain badges outside of challenges, so I'll try to submit. The blog post linked is one which I think fits the criteria well, it shares a piece of experimentation/learning that I conducted myself, with a clear writeup, lot's of screenshots, references to earlier work, two screencasts, and all the code available. I have a number of other posts like this on my blog (a few of the latest ones, about searching edutech wikis, illustrating web clipping functionality of my research system, and describing an API to see if an article is open access.