First, invest in a really nice three-ring binder with a cover sleeve where you can insert your name and vital contact information. Second, formulate a plan for the organization of materials in your portfolio, such as career summary, mission, and goals; resume; skills sets; samples of your work; testimonials; awards and honors; transcripts; and other career-related information. Third, develop a table of contents. Fourth, using dividers or some other clever method, place your material directly into the binder or in plastic sleeves made for three-ring binders. I suggest keeping the originals in safe-keeping and placing duplicates (or high-quality copies) in your portfolio.
You really need only create one portfolio. The idea is not that these are disposable, but of lasting quality. Besides making a great first impression and showcasing your skills and abilities, the other great advantage of a portfolio is that it gives you a reason to see the employer so that you can retrieve your portfolio after the hiring manager has had a few days to review it.
Finally, there is something to be said with how you present your portfolio in an interview. Dont just simply lay it on the desk in front of the hiring manager. Wait for a question to arise, such as a question about your level of skills or technical expertise, where you can pull your portfolio out of your briefcase and walk the employer through it.
You can find more details and ideas in my article, Your Job Skills Portfolio: Giving You an Edge in the Marketplace. And one more thing: portfolios do not just have to be print volumes; more job-seekers are also developing portfolios on the Web and on CD or DVD.