A cloudflare hosted task and wiki deployment - https://tajd.github.io/projektor/ - free to host because it's on your infra on cloudflare. Built it because I could, and it was simpler and cheaper than using atlassian etc.

A tool for enforcing code architecture and conventions - https://tajd.github.io/cofferdam/ - these sorts of tools come along every week, but this one is mine and it's v quick to run and extendable.

And then I'm currently working on a game for winning the start of sailing races as that's quite a tactical and fun problem to break down. Will be releasing something there soon!