I used to have a website for my UTAU works, but it was ugly and hard to manage, so I sort of abandoned it. It still exists, and somehow, people still find it....
Most recently though, I just rely on the fact that I release stuff to youtube and soundcloud. If I want to see what voicebanks or USTs I have, I just check my page. Also, LEXYS is merely a sub-page to my vocalsynth tumblr blog.
As a form of marketing for a specific UTAU or project, a good website would be quite essential. It provides a central place for all information to be gathered, yeah.