Bear's advice is very sound as far as it goes.
You probably won't be writing too many direct servlets or JSP pages in a job, but a lot of the J2EE technologies either use servlets directly (Spring MVC does I think) or require an understanding of them. JSP is less used these days, but a lot of the 'Java' exams you will take interviewing for Java positions will contain JSP questions, even though JSP isn't really Java. I just took such an exam Tuesday, and more than 10% of the questions were about JSP even though JSP wasn't on the job specification!
My feeling is that Java is losing market share in the web programming area to other technology stacks; one sees many fewer specs requiring Struts2 than a few years ago for Struts, for example. I'm actually seeing more demand for Spring MVC in my area than for Struts2! But in web programming I see a lot of demand for the Javascript stack (Javascript. Ajax, DOM scripting, JQuery, Prototype, scriptaculous, etc), and this is also a very exciting area, with a lot of innovation in recent years. XHTML and CSS are important no matter which web technologies you use. Then there are PHP and RonR (Rails), but this wanders far afield from J2EE.
I found the various Head First Books on HTML/CSS, Javascript, and Ajax to be a good start when I began with this. For Prototype/scriptaculous and JQuery look no further than Bear's books for Manning Press (Prototype/scriptaculous in Action, JQuery in Action). They are among the best. If you are a glutton for Javascript have a look around for anything written by John Resig, who founded the JQuery library.
Spring and Hibernate aren't necesarily 'hot' the way they were a year or two; they are simply necessary background for any J2EE programmer who hopes to do it in the long term. Spring has a number of subprojects which are worth digging into.
Web servers you shoul know include
Tomcat (absolutely required) and
JBoss. Lot's of demand in my area for Websphere. Portal products seem popular, as are the SOA products from IBM (Websphere) and Oracle (formerly BEA Weblogic family).
On the bleeding edge of app server technology is the OSGI spec. Spring has released a couple new containers, most notably Spring dm Server, which seems to be an OSGI-compliant server. This is the bleeding edge in containers now I think.
Apart from that I think it's worthwhile learning a range of technologies outside of Java. One of my goals is to go over to the dark side this year - learn something about C# and some of the slicker .NET stuff (Silverlight, Linq, etc). Can't say I know enough about this stuff to give a useful opinion (perhaps Bear knows more). And I'll probably pick up and do several of the Head First books on C#, Rails, and PHP this year. Java is no longer the beginning and the end, one needs more tools in one's skillbox these days.
