The ASF is made up of nearly 150 top level projects which 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.
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.
Java Caching System
Comprehensive Caching System
Apache Wicket is an open source Java component oriented web application framework.
With proper mark-up/logic separation, a POJO data model, and a refreshing lack of XML, Apache Wicket makes developing web-apps simple and enjoyable again. Swap the boilerplate, complex debugging and brittle code for powerful, reusable components written with plain Java and HTML.