Web application development in general is a hot spot. If that's an area that interests you, that's one reason that it's really
really important to understand Servlets and JSP thoroughly.
After that, you might want to explore other layers in the web app stack. For example,
JDBC for database access. Then perhaps tools like Hibernate that are popular. I personally avoid large frameworks like
Struts and Spring as unwieldily and more trouble than help, but knowing these technologies will not hurt your resume.
JSF is an abomination in my opinion, and it's unclear if it's going to go anywhere, so I'd steer clear of it for the time being.
If the client side of things interest you, HTML, CSS and JavaScript are deeper subjects than most people think and there's a lot to learn there.
And then, of course, there's lots and lots of areas outside of web apps.