The Java Special Interest Group is working on an implementation of HL7 v3 from the ground up. We have implemented all of the HL7 v3 data types with most of their operations (including the dreaded GTS). We also have Java interfaces for the RIM classes and "implementations" of the RIM classes as Java Beans. We have a MIF driven XML message parser and builder and a persistence layer using Hibernate.
Here we should add documentation and FAQs.