On the writing forums, I recently asked people to share some of their portfolio tips for freelance writers to be shared here on the blog. We had just one taker, Matt Finley of A Musing Scribe. Here's what Matt has to say about writer portfolios:
"1) Let the readers get touchy feely with your writing samples.
Instead of posting your articles on your own site, post a teaser, title and where it was published, then link to the full article where it was published.
Many writers do more than one thing. I, for example, write, program (many languages), do graphics (2d and 3d, including 2d and 3d animations), and am an instructor for things like CAD/CAM, graphics, programming etc). It's important to not only keep your different skills separated, but to also keep them linked together in an obvious but not obnoxious manner. You never know what they might be looking for in addition to what they're at your site for."
Check out Matt's writing portfolio as an example to help set you in the right direction.