The way you're going to be building credibility is through guest blogging. Editors and bloggers now welcome free (well-written and good) content. It's a great vehicle for you to catch the eye of potential employers, clients, or strategic partners.
A journalist I once cold e-mailed told me, "Always be pitching."
While I suspect that this may have been J-school 101, this crucial idea was essential to whatever results I've achieved today. Whether you're an entrepreneur looking to get your startup out there, a blogger trying to gain exposure, or a student shooting for a publication, always be pitching.