Why do you want to carry on learning?
Because you don't like your current job?
In which case it's really down to you to decide what you would rather be doing, and, indeed, what it is about your job that you don't like.
Because you want to earn more money?
In this case you need to see how people around you get promoted, or look at the job sites to see what are the requirements for more highly paid jobs elsewhere. It may be that it's actually more or different experience you need rather than more learning. But you might also find that if, for example, you wanted to move into management that requesting management training highlights nicely that you're someone to watch.
Because you like your job at the moment but think yuou might be bored soon?
In this case talk to more senior people around you and find out what they know that you don't. You're probably in this case looking at industry specific training which they can best advise on.
Because you just like learning new stuff?
That's the best position to be in because you can study whatever you like! And useful further learning can be at any level, it doesn't have to go Degree -> Masters ->PhD. Since my degree I've done all sorts of stuff including C&G Amateur Radio and A level Psychology, all of which were not only interesting but have also helped me out at work.
With a bit more of a clue as to what you're looking for we might be able to help more.
Andy Millar CEng MIET CMgr MCMIhttp://www.linkedin.com/in/millarandy
"The aim of argument, or of discussion, should not be victory, but progress." Joseph Joubert