Here's something that'll get me to buy, really. A website that is NOT about you, not about your book, but about something I'm interested in that might be connected to your book. Give me something for free that I value (that is, not author biography, which I find counter-productive often enough... I really wish I didn't know that Ezra Pound was an anti-semite Mussolini fan).
Photos of Norman castles.
Advice on how to get stains out of the carpet.
A compendium of different methods used for time travel. Well, okay, used in books. Or that could be used for time travel.
Southern dessert recipes.
Irish toasts (original language and translated).
Funny titles for country music songs.
I mean, really, there are websites about everything. And if I'm reading your website about Scottish plaid patterns and you have an excerpt from your Scottish historical novel and a link to Amazon, I might very well buy. After all, I've already gotten something from "meeting" you, if only the knowledge that the Todd (my family) tartan is actually the Gordon tartan, and so I'm related to Lord Byron (a Gordon). So I might repay it by buying your book.
That's the premise of the book The Long Tail, which I bought after reading his free advice on his blog. Give something away, and many recipients will buy something else. (Think of how many CDs and albums you paid for -- before Kazaa, I mean :-- after hearing a song for free on the radio.)
What else has worked for writers?