I'm happy to announce that Processing.js version 0.5 is now available for download. This release fixes many bugs and adds new features, including the first support for WebGL based 3D functionality (PMatrix3D, box, camera, etc.). Please note that you'll need a WebGL enabled browser (e.g., Firefox nightly as discussed here) to use these 3D features. See the changelog for full details.
Our focus continues to be on keeping the release cycles short (0.4 was released on Feb 3) as we close in on 1.0, which we anticipate releasing in early May. As a result, now is a very good time to test your code and file bugs when you find things are wrong, slow, etc. We work in the #processing.js irc channel.
We're seeing more and more people doing interesting things with Processing.js, from putting it on the iPhone, to using it to teach Game Development to university students, to creating real-time interactive visualizations on the web. It's great to see, and we look forward to unlocking much more functionality and speed in the coming releases.