Here's some (unofficial) tips on how to learn Fuse ESB:
- Take the training from a vendor like RedHat.
- Read books like Apache Camel Developer's Handbook or Camel in Action.
- Check out videos on You Tube by Red Hat Engineers and other vendors
- Check out this web site - http://www.enterpriseintegrationpatterns.com/ . This web site has the best collection and pointers to articles and theories for EAI (Enterprise Application Integration). You can also download Visio stencils to create Camel Notation diagrams like Queues, Content Based Router, etc.
- Check out github for code samples and also from RedHat web site.
The above material is a wealth of knowledge for Fuse ESB, Apache Camel, Apache CXF, ActiveMQ, Karaf and ServiceMix.
You should also go through the JEE specs for learning OpenJPA, Hibernate, JAX-RS and JAX-WS at the minimum for developing any bare minimum open source applications.
Happy Reading :)