http://code.google.com/p/pojosr/

"A service registry that enables OSGi style service registry programs without using an OSGi framework." 

Basically, it takes any jar deployed to it and treats it as an OSGi bundle, even if it doesn't have the right manifest. This allows to get the benefits of the OSGi service framework without the need for customized jars.

Here's what Peter Kriens (the OSGi architect) thinks of this: http://www.osgi.org/blog/2011/04/osgi-lite.html