Well, I guess a Java Web Start application would be the closest thing to an applet from a development and deployment prespective.
Although such an application isn't embedded in a webpage, whereas an applet is.
If you don't mind wondering into the realm of server side applications you could have a look at frameworks like Google Web Toolkit (GWT).
Build a man a fire, and he'll be warm for a day. Set a man on fire, and he'll be warm for the rest of his life.