I used to not think that a self-promotion site was necessary or even beneficial. But it has increasingly become more and more necessary. If nothing else, it shows that you have at least somewhat mastered an essential piece and basic concept of the new economy: the website.
I plan to use my other website http://www.jon-fletcher.com/ for a short bio, resume/CV, work/writing samples, and contact information, basically an internet business card. We'll see how it turns out! The sites not up right now, but it should be soon.
In case your interested, it costs about $10 to register a domain name (reserve it), and about $4-9 bucks per month to have it hosted (so that you can actually add content to it). Not a bad investment if it leads to job opportunities or career advancement.