There are a lot of resources available to help us learn about Java, starting with Sun's Java Home Page. This is the official Sun Microsystems access point for all Java-related information. You can find everything from Sun's Latest Java Announcements to Sun's Online Java Documentation to Sun's Java Development Tools.
Sun keeps the Java site fairly up to date. However, some of the language documentation has been allowed to get rather stale at times. Hopefully, with the release of the The Java 1.0 Developers Kit, out-of-date docs will become a thing of the past.
Be sure to read these pages with a Java-enabled browser so you can enjoy a
steaming cup of Java (courtesy of a Java Animator Applet).
For those who just want to download stuff, the attendant anonymous ftp site is Sun's Java FTP server. Though do note that Sun's Java servers are all heavily loaded pretty much all of the time. You may want to check out one of the many mirror sites:
Online discussion about Java is mainly conducted on the Java Newsgroup comp.lang.java. It is inundated by a huge number of posts (so I hope you have a good, threaded newsreader). The HotJava Alt Newsgroup also has a fair bit of discussion. It is less busy than the Java newsgroup but it gets a lot of non-HotJava related posts. The JavaScript Newsgroup was recently created for discussion of JavaScript issues. The traffic seems pretty light so far and seems to be staying focused on JavaScript.
There are also some Java-related mailing lists. Sun's Java Mailing Lists are mostly holdovers from the days before the Java newsgroup was created. The Linux Java Mailing Lists are about porting Sun's Java Development Kit to the Linux platform. There is also a (wonderfully low traffic) mailing list discussing the development of a "real-time" version of Java at real-time-java-request@iastate.edu. Some of the lists are quite technical. The announcement mailing keep you informed of new releases. Unfortunately, the Sun Java announcement mailing list gets very little traffic.
Digital Espresso (once known as "J*** Notes") was created to distill the flood of information from the Java newsgroups and mailing lists into a concise summary. Digital Espresso's team slogs through all of the comp.lang.java posts and distills the important information into a relatively short weekly report. This is a great resource to keep abreast of the major flow of comp.lang.java but is not, of course, a substitute for active newsgroup participation. Since Digital Espresso tracks all of the Java-related announcements, it is a great substitute for general announcement mailing lists.