Code Review. A community that learns as it grows, and grows as it learns.
weekend-challenge projects are a huge opportunity to learn from each other. As individual coding marathons, these projects are fun.
Here's the proposition: each weekend-challenge project gets a dedicated GitHub repository, where the canonical implementation comes to life; each "winning proposal" for a weekend challenge becomes an ongoing community project.
And then we can have other such community projects, like we could write an API for SE Chat, or whatever we as a community, decide we should come up with.
It's possible such an idea would not be possible because it would/could affiliate StackExchange with GitHub and we don't intend to instigate that. I wonder if, if not officially SE-stamped, we can do this.
When someone has code to commit, the modified class(es) can (should!) be posted on the main site to be reviewed by anyone; the CR question would need to be Community Wiki, and link to the GitHub repository, and the code that isn't the OP's code should be in a quote block.
Any other ideas? Objections? Suggestions? Unicorns?