portfolio building, working for closed-source vs open-source? [closed]

Question

I've currently graduated from my first run at higher education, landed my first full-time gig as a web application developer, and absolutely love it.

My question is that in looking for jobs I ran across many jobs that require a certain level of experience and code examples. Much of the work I am doing is both protected by a login, and closed source. How does someone, that is just starting out and needs to be building a resume, go about preparing for the next job.

(no matter how much I love my current job, I feel like it's only responsible to always be preparing)