Any repository from weavejester (James Reeves) Very high standards

https://github.com/ring-clojure/ring

I think that's a tough one, most repos will be doing something pretty specific, with arbitrary preferences, and subject to "real-world pressures"

So a better kind of candidate would be "code katas", these often come from TDD workshops or courses. Even if you're not into TDD, I'd wager the code/tests/commits would be more useful than an arbitrary repo's