The Apache Portal Project has posted the first release candidate of Pluto 1.0, the open source reference implementation of the Java Portlet Specification. According to the announcement,
The Java Portlet Specification defines a Portlet API very similar to the Servlet API. The API provides means for aggregating disperate content sources. The specification addresses security and personalization considerations and defines a standard with which these sources, or portlets can be deployed.
Pluto is an embedable portlet container which will typically be bundled within a fully functional Portal. The Pluto community has developed a simple portal driver implementation which allows for the testing and development of portlets with the container. The Pluto testsuite is an implementation agnostic portlet application which tests several basic operations of the container in which it is deployed.