ActiveSpace
* a simple to use toolkit for building distributed systems reusing powerful messaging middleware and transactional and clustered caching
* supports two core abstractions
** Spaces which provide a JavaSpace-like abstraction for building grid based applications easily 
** Caches which provide full support for transactional and ClusteredCache support. 
* is specifically designed for high performance messaging, clustering and grid computing using a simple set of abstractions allowing things done quickly without complicated middleware or infrastructure
* Web Link
** http://activespace.codehaus.org/.