An Introduction to RDF and the Jena RDF API
I have been busy for the past couple of weeks starting to write some semi-serious Semantic Web code in Java. Most recently I have been parsing, manipulating, and generating Semantic Web RDF data using the Jena open source library. Although I have already gotten some code up and running using Jena (generating and writing my own FOAF profile and crawling FOAF profiles), I still have not yet finished reading the basic Jena tutorial: An Introduction to RDF and the Jena RDF API by Brian McBride, Daniel Boothby, and Chris Dollin.
This tutorial is quite readable and does encourage you to jump off and do some actual code prototyping, which is what I have been doing a lot of. Unfortunately, for all the code I have written, I have still not read the turorial front to back. But now that I have so much code under my belt, filling in the many knowledge gaps is a higher priority. In any case, I recommend the tutorial, both for Jena and as a basic intro to RDF itself.