Ubuntu Intrepid, released today, includes the newest version of java, Java 6 update 10 build 33, which features a new java browser plugin with support for features like draggable applets and jnlp-based applets. See these demo applets, for example.
For some reason, however, Ubuntu still has the old version of the java plugin enabled for browsers. So those demo applets won’t work. And how to get it to work is not documented correctly anywhere. To make it work, run these commands in Terminal:
sudo update-alternatives –install /etc/alternatives/xulrunner-1.9-javaplugin.so xulrunner-1.9-javaplugin.so /usr/lib/jvm/java-6-sun/jre/lib/i386/libnpjp2.so 50
sudo update-alternatives –config xulrunner-1.9-javaplugin.so
and select the libnpjp2.so option (2)