Regex pattern-matching in 15 lines (here via @swannodette). The hits keep on coming from David Nolen.
Solving the mapping dilemma (here via @swannodette). David Nolen explains how working with the match library he got the level of abstraction exactly right, and produced super fast code in the process.
Briefly, the “arity-reduce” pattern in Clojure (here via @maclausen). Dave Ray shows how using multiple arieties in your functions results in cleaner code.
Clj-watch (here via @maclausen). Small script that auto-compiles your ClojureScript files upon changes.