I recently read an article on A List Apart called Help! My Portfolio Sucks! I thought it was a great piece, but I didn't think it went far enough.
The submitter wrote to say that they were unhappy with some of the work in their portfolio - that what the client wanted wasn't as awesome as what they would have done if they had full control. Or, that as the web got cooler, some of the older pieces started to look stale or outdated (they'd no longer impress). The response noted that you don't have to include every piece in your portfolio and that if necessary, you could also do some side projects to show off your skills, even if they weren't for a client.
They touched on it briefly, but I think that they didn't speak enough about context. One would presume that no matter how you personally felt about the work, that you were pleasing your clients. If not, that's a bigger issue.
But if the clients were happy, then you were successful, even if you were unhappy with the final outcome yourself.
And this is where context comes into play. The work itself should not stand alone. You aren't marketing the client and you aren't hoping that you can make the sale by simply pointing to your past work and asking your clients to figure it out.
No, you're asking the prospective client to embark on a journey with you, hopefully one that will last over multiple engagements. You're only successful when they're successful, it's easier to retain a client than acquire a new one, etc., etc., etc.
So you take these pieces of your portfolio and you give your new prospective clients perspective. Here's what the client asked for, here's how I delivered and here's how I went above and beyond. If we were to do a future phase to this work, here's what I would encourage the customer to consider.
Show that you can deliver. Or to put it another way, even if the customer wants a pizza with anchovies and only cheese on half, even if that disgusts you and all the other customers, you can still make a great pizza and tell the story of how happy the customer was when you delivered exactly what they ordered, even taking the time to make sure the crust was evenly golden all the way around.
This isn't about them and it isn't even about the work. It's about your ability to deliver.
I like how this company, Rational Interaction (portfolio) sets each page up with a common structure: here's the challenge, here's how we applied our approach, here's the results. It's easy for a new prospective client to imagine how RI would go about solving their problem. (I have no connection to RI.)
So get out there and sell yourself.