sayid: A powerful tracing/debugging tool. It is a great alternative of CIDER-nREPL’s basic tracing functionality.
scope-capture-nrepl: A companion library to scope-capture, providing an nREPL middleware that lets you put your REPL in the context of an Execution Point.
This section lists middleware that were somewhat prominent in the past, but were replaced by alternatives down the road.
nrepl-middleware, part of ritz that provides a variety of nREPL middleware supporting various enhanced REPL operations (including apropos, javadoc lookup, code completion, and an alternative eval implementation). (superseded by cider-nrepl)
Javert provides a basic object inspector. (superseded by cider-nrepl)
nrepl-profile: profiling middleware, which was eventually integrated into cider-nrepl.
This list doesn’t aim to be complete. You can find more 3rd-party middleware listed here.