Consider what ravelry.com did. It’s a social networking site for fiber arts – knitting, spinning, crocheting.
They built the site, and included an “invitations” feature. You can sign up for an account, and they invite a certain number of people a day, to make sure they can scale controllably.
Then they invited several of the best-known crafting bloggers (Grumperina, the Yarn Harlot) to take a look at what was there.
The end result was that the bloggers wrote about how cool it was, and then when people read about it and heard about how cool it was, they found that there was a waiting list. Oddly enough, this didn’t deter them, but gave them something to talk about—“oh, I’m #2105 on the Ravelry queue!” “You lucky bum, I’m #7154!”—thus further spreading it via word of mouth.
So consider who the target market for this website is, and what their patterns of interaction are. Is there an online community (or, better yet, several online communities) where people likely to be interested in your product hang out? Is there something cool you can do to get people in those communities to talk about you?