Booksquare has a great series of articles on how to build your own writerly website. Worth reading even if you have a site already.
All I have to add to the thing is a kind of table of contents:
1. The beginning: getting your own domain.
2. Once you have a site, think about your audience.
3. Start a conversation with the other kids: link, link, link.
In a similiar vein, via The Emerging Writers Network: the beginner’s guide to publicists, and the refresher course for veterans.