Glassfish v3 TP2 supports already some EJB 3.1 features (spec is not finalized yet) - and it is embeddable. Check this post for details. This opens some new interesting opportunities and use cases. An obvious one is unit testing, another one ...the direct usage inside of RIAs (Eclipse / Netbeans RCP) - I will present some more ideas in detail during my session at Friday (JavaONE).
NEW online workshop: Web Components training (online)