There are two answers I always have to the "what should I make first" question.
First, make a blog. It's the tried and true method for learning most frameworks. Plus, you can blog about the things that you're learning, as you're learning them. For every person who asks these questions, there's easily a dozen others who are asking the same exact things in their heads.
Second, think to things you'd like to have, or something you think you could do better.
For instance, I hate that there's no really easy Knowledge base as a service thats not tied to a full help desk suite. I don't want to pay for all that, I just really need a FAQ section that's easily editable. That's something to make.
Or maybe you wish Twitter sorted things by character count rather than date. Make a Twitter clone that does that.
Those are obviously not great examples, but you get the idea.
Build on, builder!