As creative professionals, we all need a portfolio, or in advertising, a "book." You keep it updated with your best stuff, and you send it to people so they'll hire you.
Long ago, people (probably the people you'll be sending your book to) used to make these by hand, out of real-life paper and cardboard. You still need to have a physical version of your book so the people interviewing you can look at something other than the growing sweat-stains under your arms. However, for sending it out with a letter and resumé, nothing is more convenient than an online version.
That being said, there are lots of online portfolio services. I have my favorites, but I wondered if there was a better version, so I did some searching. Guess what? Lots of these places want you to pay! And as I always say, why pay for something you can get for free.
www.carbonmade.com is my personal favorite, as you can see by clicking the My Portfolio link to the right. It has a free version, which allows 5 projects and some number of images, and a $12/mo version that gives you a lot more of both, plus videos. Even the pay version is cheaper than the other portfolio hosts I saw.
www.behance.net is a portfolio site, plus a professional networking site. I like it, but I like carbonmade more. Behance is a little more byzantine when it comes to adding projects, but I don't think there's a limit to how many you can add, and videos are FREE!
I also used to be a fan of www.deviantart.com. However, I fell out of love with it. But it's out there, so here ya go. If anyone has a better option, feel free to drop a comment in the ol' comment box.