[YeGoblynQueenne]

Hey. My advice would be to not try to code something "useful" but something you personally want to code, like a game for example, or a compiler for your own programming language. A game is a good idea because it will give you the opportunity to learn lots of advanced techniques. A programming language also (and you have already built a compiler, which is a start) and it will also make you look properly geeky to potential recruiters.

But the important thing, now that you're not at uni anymore, is to find the time and the energy to write as much code as possible and perhaps read as much of others' code as possible.