I would also like to recommend Thinking In Java as well. It's kind of like the Perl Cookbook, in that it teaches you how to figure out how to do what you want to do based on the best way to do it in the language. I believe O'Reilly has a new book called Java Enterprise Best Practices which handles the same kind of thing for RMI, EJB, servlets, JDBC, XML, Java management extensions, internationalization, JSP, JavaMail, and tuning (I'm reading this off the table of contents from safari.oreilly.com - I am so not an expert in any of this!).