In no particular order.
- JSON: https://github.com/dakrone/cheshire
- Templating: https://github.com/weavejester/comb
- Web server: https://github.com/ring-clojure/ring
- JDBC_DATABASE_URL env var in Heroku: https://devcenter.heroku.com/articles/connecting-to-relational-databases-on-heroku-with-java
- Composing infrasturcture and interactive development: https://github.com/weavejester/integrant
- Embracing SQL in Clojure: https://www.hugsql.org