If appropriate (the key words here being "if appropriate"), feel free to bring samples or copies of your work to the interview as concrete examples of your capabilities. Use reports, projects, photos, programs, or whatever it is that provides a tangible example of what you have done. It's one thing to say "I developed a report," and quite another to actually show the report you developed. You can incorporate several samples and examples into an effective job portfolio.
While the types of samples you use may vary, they can include information developed either through capstone-level classes or work projects.
Following are a few examples that have been used successfully:
Be fully prepared not only "to show" but also "to tell" about your sample. Be ready to answer any and all possible questions that might come up. This should not be a casual sample—it should be an example of your very best work. It will stand as the icon of what your capabilities are. If you are extremely proud of something you have done, show me—and tell me why.
Telling me what you have done is not nearly as impressive as showing me what you have done.
If possible, you might want to consider using your show-and-tell samples as "leave-behinds" for the company to look at later. There is usually not enough time within the course of the interview to fully explore a good show-and-tell item. This also puts another hook into the company for necessary future contact.
Although using your sample as a "leave-behind" should only be done if the item is reproducible, you might want to consider leaving behind sample only items with an employer, if you are truly interested. Tell them: "I'll just pick it up when I'm here for my next interview" or (if this is your final interview) "I would be more than happy to pick it up on my start date." Presumptuous? Possibly. But it may also be your golden opportunity to close the sale!