OK, today I try to learn JAXB. Let’s forget for a moment that XML generation and parsing is such a trivial task that adding this type of abstraction only makes it 100 times harder to understand, debug and work with. But hey, I am not always given a real choice..
The unofficial guide seems decent (but is actually just a bunch of xml lovers hugging piles of xml file references to other xml files, with couple of pearls in there): http://jaxb.java.net/guide/
For Java to XML mapping this is brilliant: http://stephou.wordpress.com/2010/01/20/convert-java-objects-to-xml-with-jaxb/
And when someone creates a JAXB class without understanding or wanting to understand what it maps to (whooppee for the benefits of XML there)? Well, JAXB comes with schemagen that allows to generate the XML schema
and finally the rest of the docs including the tutorial are ok even if a bit verbose: http://jaxb.java.net/tutorial/