If you work in marketing (or PR for that matter) and commission design, you might be missing a trick.
There comes a time to move on and look for a new job. Most people will update their CV and Linkedin profile and be done with it. As I say, you are missing a trick.
If you have commissioned and managed agencies, instigated campaigns, overseen website builds and created strategies, then I believe you should show the results. How you do that is up to you.
My company, Navig8, offers to help a client when we hear they are moving on. That means we offer, we don't wait to be asked. We don't charge them either. We do say something like 'buy us a drink'. If we do get together for a drink, it helps saying goodbye and means our agency is in their mind when they start their shiny new job.
Firstly we gather up every asset from the projects we have worked together on. Every PDF, screenshot, every jpeg. If your filing and job tracking system is good (see: Know Your Onions: Graphic Design) then this is no great shakes.
We don't use the high-res files, the artwork files, but the last proof that got sent to the client for sign off. These are low-res. We then burn them a DVD and send it to them. This is better than emailing or transfering the files. We have nicely branded DVDs and the client can refer back to them, every time being reminded what a nice agency Navig8 is.
Then we design them a nice PDF portfolio. Each page(s) gathers up all the activities for that campaign or project. We design it for them, not for us. So we focus on campaign reach, diversity of channels of delivery etc. Sometimes we include stats and screenshots showing reach. For instance a number of tweets or sign ups, or just good old fashioned SEO results.
Your client might not realise or imagine how this might look, so you may need to do this for them. Remember, this is not an agency portfolio, it is a client portfolio, and its aim is to show their potential employer how they managed you (and others) to deliver a brilliant job.
The end result is to give your client the edge at an interview. Something visual, tangible and demonstrative. And of course, keep them happy.