This is very subjective, but here goes.
- It wouldn't hurt to know a very corporate language, like Java, for web development.
- Learning a framework for it, like Spring MVC, would be very handy. Spring also has concepts like AOP and IOC, worth knowing.
- Adding in Hibernate for DAO/ORM would be useful.
- Ruby on Rails (Ruby is the language, Rails is the framework) is another web development track.
- Sometime during a programming career, you'll need to know one scripting language; Python or Perl.
- Learn tools like Maven or Ant, Subversion or CVS, and make sure you know how to use an IDE, like Eclipse.
- If you don't know Linux, that can be fun to play with and useful professionally. Try Ubuntu.
- From a theory level, learn about Data Structures and Design Patterns.
Data Structures is usually the second university course in computer science, and will almost certainly help your coding. If you build examples to teach yourself this, use a language you don't know yet, so that you gain both knowledge of a new language and knowledge of new theory simultaneously.
There are online references for learning the material. You should be learning about linked lists, trees, and graphs; sorting, searching, and O(n) analysis.
From a hiring manager's point of view, I wouldn't interview anyone without demonstrated knowledge of data structures.
In any case, Project Euler might also help you; it's a group of programming tasks designed to help you learn new languages and have tasks to help you solve new problems.