The ASF is made up of over 100 top level projects that cover a wide range of technologies. Chances are if you are looking for a rewarding experience in Open Source, you are going to find it here.
A modular, full featured XMPP (Jabber) server
Apache Vysper aims to be a modular, full featured XMPP (Jabber) server. Vysper is implemented in Java.
Server-side Tcl programming system combining ease of use and power
Apache Rivet is a system for creating dynamic web content via the Tcl programming language integrated with Apache Web Server. It is designed to be fast, powerful and extensible, consume few system resources, be easy to learn, and to provide the user with a platform that can also be used for other programming tasks outside the web (GUI's, system administration tasks, text processing, database manipulation, XML, and so on). In order to meet these goals Tcl programming language was chosen to combine with the Apache HTTP Server.