XmlBlaster is MOM (Message oriented Middleware) with a lot of features.

XmlBlaster is a publish/subscribe and point to point 100% Java based MOM server
(message-oriented
middleware) which exchanges messages between publishers and subscribers. The
message is described
with XML-encoded meta information. Messages may contain everything, GIF images,
Java objects, Python
scripts, XML data, a word document, plain text - just anything.

Communication with the server is based on socket, CORBA (using JacORB), RMI,
XmlRpc, HTTP or email,
clients are free to choose their preferred protocol. Other protocols like SOAP
may be plugged in.

Subscribers can use XPath expressions to filter the messages they wish to
receive.

This is the publish/subscribe middleware server you have needed many times
before, now available for
free to glue together your distributed client/server application.

The xmlBlaster server is pure Java and under LGPL.
PHP, Perl, Python, C, C++, C#, Visual Basic.net, Flash, J2ME, Java
(applications, servlets, applets)
client samples are delivered in the xmlBlaster distribution.

http://www.xmlBlaster.org