First off, lets make sure everyone is on the same page here and understands that your portfolio (be it freelance or for your company) is THE most important tool you have. Yes, its a tool. Its a way for clients to see what you can do. Its a way to convince them that you can complete the work that they desire. It helps get conversation started and it helps seal the deal.
Your portfolio starts conversations and opens doors when it gets passed to potential clients and they are impressed by your work. You want them to think "Shit, that is badass. We need something like that." Sorry for the foul language, but the client was impressed and couldn't help it. This type of reaction is what allows you to begin to network and develop business with potential clients that previously did not know you even existed.
On the flip side, the portfolio can seal the deal when the client comes to you with an idea but wants to be convinced that you can complete the work. This is where your portfolio needs to be filled with projects of quality and caliber that is similar to the ones you are going after. If the client is looking for an interactive game, you sure as hell better include some games in your body of work. Verbally saying, "Oh yeah, we can do that. We have a Flash guy." may work for the inexperienced, but it is not going to land you jobs with the big fish. You need to prove that you can do it and the best way to prove it is by having already completed similar projects before. You got to see it to believe it. This proof is one of the best ways to seal the deal with a potential client.
Now that we covered why we need a portfolio... how do we get clients to say "Shit that is badass" and prove to them that we can do the work they want? The most obvious thing you must include a collection of previous work. By definition, that is what a portfolio consists of. However, as obvious as this step is, it can still be fucked up. First off, don't include every piece you have ever completed... only include your most recent and your best. Each project should have a reason for being in your portfolio. Whether it shows that you can work on a national campaign, that you can do 3D, that you can make games, etc... Each piece should show a different side of your work. DO NOT INCLUDE EVERYTHING! If you don't want to do banner ads, don't include any banner ads in your work. If you don't want to do print design... don't show it! Fill your portfolio ONLY with the type of projects you enjoy doing and want to continue doing.
The next step in proving your skill set is including verbiage that describes what your role was on the project. This is important because you may not have worked on every aspect of a project and you need to be clear which parts were your own and which parts were done in collaboration. The goal here is to be very clear about what you specialize in and not leave clients wondering what your capabilities are.
So you have your focused body of work w/ detailed descriptions all ready to go. The final question, and one of the most important ones, is how do you display this information? You can get by with a clean and easy way for users to find your work and cycle through them. However, making your portfolio a piece of art in itself will take it to a whole new level. By making it a piece of art you are doing two things. First, and most importantly, you are giving yourself a chance to strut your stuff. This is your chance to flex your muscles with no client restrictions. Use this opportunity to prove to clients that you can do work that they may not see in your portfolio. If you want to prove that you can make a game but you don't have a full game in your portfolio... make your portfolio a game. That is what I did back in 2005 (www.ickydime.com painful to see now, but you get the point). Second, by strutting your stuff you are increasing the chances that the potential client will think your portfolio is "badass" and therefore increase the chances they will reach out to you. No matter how polished your previous work is, if it is not presented in a quality manner then the client will be distracted by the presentation and think less of your overall work.
In summary, a successful portfolio is one that "wows" clients, proves to clients that you can do the work, and ultimately leads to more work for yourself and your organization.
Using this definition, does your site qualify as being successful? Does it show the type of work that you would like to continue doing? Is the site a portfolio piece itself, or does it just present your work? What does it do well? What could be improved?
For full disclosure... here is The Basement Design + Motion's most recent homepage and portfolio. The site showcases different design styles and disciplines (3D, Motion Graphics, Interactivity, etc). Every team member had their hand in the project at some point or another.
Do you think this site qualifies as being successful? What does it do well? What could be improved?