I've finally gotten around to building my portfolio site. It's only been seven years.
A chronic problem, I think with developers, is that we don't usually think that a portfolio site is necessary - and this is probably true. I think, however, that if on my next interview, this site is visible and available, I will be far more likely to be asked, "What was your role in Project X", rather than, "What projects have you worked on?"
I find the former to be an easier question to address, as it's a specific description of things I like to do, rather than a nebulous inquiry into the haze of past accomplishments.