REPL - Is in Russian but describes why REPL development is so amazing.
cljfmt - Tool for formatting Clojure code.
clojure-lsp - Language Server (LSP) for Clojure.
kaocha - Full featured next gen Clojure test runner.
Manifold - Compatibility layer for event-driven abstractions.
REBL - Graphical, interactive tool for browsing Clojure data.
Virgil - Your own personal JVM psychopomp.
Luminus - Clojure micro-framework based on a set of lightweight libraries.
clojerl - Clojure for the Erlang VM.
edn - Extensible Data Notation. Superset of edn is used by Clojure to represent programs.