Apache Aries, WebSphere Application Server V7 + OSGi and SCA Feature Packs and WebSphere Application Server V8 all support external bundle repositories. However, a common frustration among those who use external bundle repositories is the creation of the repository. Emily Jiang, a member of our development team, recently developed a repository generation tool that's worth sharing (instructions can be found on the Apache Aries website). The tool takes a list of URLs and generates a repository xml file describing the URLs. If the given URL is a local file directory, the tool will generate metadata for all valid bundles in that directory, which saves the user significant effort, as they do not need to explicitly list every bundle in the target directory. Subdirectories will be recursed for any bundles that exist higher in the directory structure.
For more instruction about how to administer external bundle repositories, check out the docs for the WebSphere V8 beta infocenter: http://publib.boulder.ibm.com/infocenter/wasinfo/beta/index.jsp?topic=%2Fcom.ibm.websphere.osgi.express.doc%2Ftopics%2Fta_admin_obr.html