I've been a PHP developer for 5 years now. Before I started working in that field, I've been practicing at home. I've created my own CMS, so I could actually show some of my code to the potential employer. In the final version, it had about 2,000 lines of code, and no one except me was using it. But that was not the case, because I've learned a lot during this project.
Lately I've decided to move forward and abandon web developing for sake of C/C++ programming. I've read a few books recommended on stackoverflow, skimmed over a glibc manual, and solved some problems on Project Eurler as adviced. Now it's time to start some project, but I can't come up with anything.
What is the next step I should take?