Java

Not to be confused with Javascript, Java is a fully blown programming language that plenty of web applications have been written in.

Java dropdown menu
Java Dropdown Menu.

Java examples
Examples of java applets that you can download and customize for your own use.

The Java Tutorial (Sun Microsystems)
The Tutorial is organized into trails--groups of lessons on a particular subject.

Java Servlets (Webmonkey, 11 Feb 1999)
Java has come a long way since the Tumbling Duke days of yesteryear; now it's being used on the server side.

Writing Chat Systems with Java 1.1's RMI (Webmonkey, 16 Jul 1997)
A quicker, easier way to develop a chat system.