The Avalon project is Apache's Java Server Framework. It is separated into six sub projects: Framework, Excalibur, LogKit, Cornerstone, Phoenix and Applications. 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 Phoenix is a micro-kernel designed and implemented on top of the Avalon Framework. It is both an API to program to and a reference implementation. The reference implementation provides a number of facilities to manage the environment of Server Applications. Such facilities include log management, JMX management, classloading and security. The API defines a standard method of piecing togther server components and creating a server.
In order to see Avalon Phoenix at work, you should grab the example applications or servers that are included in Avalon Cornerstone. Apache James uses Phoenix for it's mail server.
For more information about Phoenix 4.0beta, please go to http://jakarta.apache.org/avalon/phoenix.