Google Guice (my favorite DI framework for Java) has a neat extension called "Multibindings" that allows you to auto-magically inject a collection of objects that implement a particular interface. This allows you to model SPI-style interfaces with ease.
Multimaps are one of the many collections in Google Guava. I describe why you might want to use them.
Spark is a new micro-application-server for Java that models itself after Ruby's Sinatra library. While it's still Java, it shows that minimalism is possible with this crufty old language.
A review of the new "Apache Wicket Cookbook": A collection of code solutions for a variety of problems in Apache Wicket.
I make the case for why the try-with-resources feature in Java 7 is a waste of time and development effort.
I walk through the type inferencing engine in the new JVM language: Mirah
Part Four in my "Distilling JRuby" series talks about the techniques for generating frames and backtraces.
The Play! Framework is a new Java web-framework that actually manages to merge minimalism and Java together (somewhat paradoxically).
I recently did some contributor work with JRuby focusing on performance problems. Here's the story.
Suprising news from Jetbrains: IntelliJ will have a free community edition!