JBoss AS7 has been released today - an amazingly fast and lightweight Application Server with built-in OSGi support. Just deploy your OSGi bundles and go!
For more information see the main AS7 page: http://www.jboss.org/as7.html
Or have a look at the quickstarts page!
The OSGi support in AS7 implements the OSGi 4.2 core specification. Thomas Diesler has contributed most of the code, and I have implemented some bits and pieces in there too... Lets us know what you think or if you find an issue. The forums are here: http://community.jboss.org/en/jbossosgi and more details on the project can be found here: http://www.jboss.org/jbossas/osgi