Mark Watson's Book

Mark Watson has a draft available for the 3rd edition of his Java AI
book. The book is and will continue to be freely available. I've
enjoyed enough of it so far to know I will happily pay my good money
for it.

http://markwatson.com/blog/2008/09/looking-for-reviewers-for-my-book.html

Very pragmatic and educational.

People not interested in "AI" per se could still be interested in
several chapters. One is on the semantic web, RDF, etc.

Another chapter on rule systems has a good section on Drools. There've
been a couple projects in our office here that had a good experience
with Drools.