Rails may not be the right tool for every job, but combined with the huge ecosystem of mature Java libraries, it can be a powerful tool.
Don't assume that Ruby is only useful for making websites with Ruby on Rails, because I've been using it for years without shipping a Rails app.
A quick work-around to get rake assets:precompile to work when using the jruby-complete.jar.
How to set up a JRuby project using the jruby-complete.jar using Bundler to manage gem dependencies.
I benchmarked some tests run in JRuby that compare the Hamsterdam library using Hamster's immutable Hashes vs Clojure's PeristentHashMap, plus some gotchas.
An example of using Celluloid Actors to provide a poor man's Ref (Clojure-like) around an immutable data structure in JRuby to protect shared state.
An FFI wrapper is much easier to write and maintain than a C extension, more portable across platforms and languages, and easier for users to install.
A simple JRuby script showing how to use the vlcj library to playback video full screen on a Linux machine.
Simple but effective JRuby code that simplifies the use of RXTX for basic serial port communications, with sample terminal.
How using Hamster's efficient, immutable, thread-safe collections can prevent ConcurrencyError exceptions in JRuby.
Using warbler-exec, we can use the .war file itself to run the migrations without needing to transfer another copy of the rails app for this purpose.
Pry features syntax highlighting, a flexible plugin architecture, runtime invocation and source and documentation browsing.