The Avalon project is Apache's Java Server Framework. It is separated into five sub projects: Framework, Excalibur, LogKit, Cornerstone, and Phoenix. Its purpose is to simplify server side programming for Java based projects. It formalizes serveral best of breed practices and patterns for server side programming.
For more information about Avalon, please go to http://jakarta.apache.org/avalon.
Avalon Excalibur contains several premade Avalon Components and utilities to make your server side programming easier. There are several pool implementations, Component management implementations, and database management implementations.
For more information about Avalon Excalibur 4.1, please go to http://jakarta.apache.org/avalon/excalibur.