there is a lot of theory on portfolios. some people think it should be one way, some people think it should be done another way, etc... so no matter who answers this thread you will get a lot of opinions, none of which are right and none of which are wrong, either.
having taught a portfolio class, my opinions are as follows:
i think that a portfolio is/should be 2 things: first, it is a selection of your work you have done into a cohesive, navigable collection to show to someone who does not know you. second, it is a narrative story about you told through what you make. therefore, there can be a few kinds of portfolios: a bunch of your work gathered together neatly, and a bunch of your work gathered together neatly and placed inside of some kind of considered, designed "thing" that tells more about you than just your work itself does.
so what does that mean? it means you tend to see a couple of archetypal portfolios out there: the boring and the overdone. the boring portfolios are just some kind of black binder thing with even sized pages of your work in it. neat, orderly, and not particularly unique as a portfolio. you also see ridiculous, over-designed things where designers try to "brand" themselves with weird colors, odd page sizes, logos all over the place, cheeky typography, gimmicky packaging (if i see one more portfolio bound in metal i will kill someone) and a lot of stuff that just takes away from the work itself, which, in an overdone portfolio, is usually somewhat mediocre.
so. what to do.
you should think of a portfolio as a book about you and your work. a monograph. go to the nearest bookstore or library and look at designer's monographs. look at what they do. look at what works. what does not. think about how the books talk about the work inside them.
if you had a client who came to you one day and said "i design pottery. i want to have a monograph made about my pottery collection. i want it to be clear and readable, but memorable. i want it to be reflective of me and why i do the kind of pottery i do." you would then spend a lot of time looking at the person's work, talking to the person, getting a feel for why they do what they do, how they do it, what interests them, what influences them, etc... BEFORE you designed the book.
now imagine YOU are the client. get to work

note that nothing needs to be overly designed, but nor should it be just a pile of stuff bound together.
so having said all that, at the end of the day if you have an interview next week and just need to get your work viewable, then do so. get a black portfolio binder, print your work out on neatly laid out pages, drop it in and call it a day. but when you get time you should consider the above.
some general things i have noticed:
-the worse the work in the portfolio, the worse a highly-designed portfolio will be.
- only show great to excellent work. DO NOT SHOW BAD WORK even if it means you only have 5 projects in your portfolio.
- show around 8-12 projects for an initial portfolio. if you get a 2nd or 3rd interview, you can show more work.
- do not show a lot of "process" or sketchy things on interview 1. wait for followup interviews for that.
- people always, always, always prefer the real thing to a photograph of the thing. if you did a brochure, bring it in. if you did a poster, bring it in.
- if you do not have the time to really spend designing a portfolio well, do not design it at all.
- engaging, not gimmicky
- descriptive, not mysterious
- clear, not muddled
- fine, top quality hazelnut gelato, not generic vanilla.
- with things like
indexhibit you have no excuse not to have a selection of work online.