I've used a few technologies in this area, I can highly recommend JBoss Cache as the best choice for what you're trying to do. It uses JGroups as its transport, but provides a higher-level transactional abstraction. Out-of-the-box it gives you a distributed tree-node structure.
edit: Oh, and JBossCache is independent of JBoss Application Server, you can use it in any environment. If anything, it works better outside of JBossAS than it does inside it.
