Widefinder 2 with Clojure - Tim Bray's Widefinder2 project is slowly delivering very interesting results, here an article about how to optimize Clojure so that the performance beats the best Scala and Java solutions so far (where the Java version can of course catch up trivially, as most performance-relevant things in this version rely on Java libraries). A nice example of how you can bring low-level optimization into Clojure for the things that are really important for performance, but still keep the good high-level mechanisms of Clojure for the rest of the code.