Where to go from being a young, intermediate Programmer?

You all know the "Hod do I start?" questions, which are asked by people who want to learn how to program or worse how to "hack". But what happens after you did everything on the list? I am now seventeen years old, I am fluent in three languages (C++, Python, Lisp), know Linux and Windows quite well, can operate hardware etc. I've also participated in many projects and competitions concerning programming and such. Soon I'll have a traineeship in a IT company producing search engines. But what should I do until I hit university (apart from improving my English)? Pack on more languages? Continue with Projects on Sourceforge? Do something completely else? How would a professional answer the question "How do I continue from here on?"?