Learn your design patterns if you haven't already. They are both technology-agnostic and [relatively] timeless. Not only will they make you a better programmer, they will make you a MUCH better interviewer IMO. Every company I've interviewed that was good enough for me to consider has asked design pattern questions.
The best source for these is the Gang of Four book, but I've heard good things about Head First Design Patterns
Don't limit yourself to just learning programming techniques. Even if you aren't a project manager/architect/technical lead your career will benefit from learning about their roles. Most people on Stack Exchange know this, but Joel on Software is a great blog that touches on all aspects of software development from the code monkey to the CEO.
I've personally been trying to improve my written communication skills. There are invaluable in many lines of work, including software development. Stunk & White is a good place to start.
EDIT: lots of answers to a similar question here.