Real world specifications for Project-Based Learning?

Hey folks,

I'm reaching out because I've hit a bit of a wall and I reckon a few brains from this crowd might have the insight I need.

I've always been a big believer in learning by doing - give me a real-world problem and a keyboard and I'll bash away at it until I get the thing working. But I've been finding that in my day job, I don't often get the chance to really experiment. Business needs and project timelines get in the way.

So here's what I'm thinking. I want to dive into a few short-term, project-based learning adventures where I get to be the architect, the engineer, the QA... you get the idea. I don't want to start a new business or anything - just want to get my hands dirty and build something from the ground up.

What I'm hunting for are some solid software system specifications. The kind of thing you might get from a client or stakeholder that has enough detail to get going but leaves room for you to make some design and implementation choices. Basically, I want to flex some creative muscle, test out new architectural patterns, and make my own mistakes - and learn from them - along the way.

If you know of any resources, repos, websites, books - anything where I could get my hands on something like this, I'd be super grateful for the heads up. And if you've done something similar, I'd love to hear about your experiences and what you learned along the way.

Looking forward to hearing your thoughts and ideas, and diving into this new challenge.