I am sure you’ve all seen the animation played by the Java plugin when a large applet loads in the web browser. Sun found it a bit outdated and decided to improve it for JDK6u1 and JDK7. Chris Campbell did the implementation work and explains a few things about it on his blog. I especially like the way resizing is handled. Note that you can override the animation if you wish to.
You can also run the WebStart version below: (Java SE 6 required)