I would find an open source project you find interesting and hack on that for a while. It will allow you to learn from code that others have written, while also creating your own.

I ran a website a while back that ran on TikiWiki, and I learned a lot by hacking on its internals. I think it's hard to start from scratch, so seeing other people's working code can be useful. However, partly it's personal preference also. There is a downside to open source, which is that you might start off learning bad habits or learning from poorly written code.