Made a page ( http://www.myspace.com/awdforums ). Just simple page telling about my site. I then searched for groups(in my case subaru and mitsubishi car groups) and I requested an add to each and every member of those groups. I now have over 700 friends who have all seen my page and about 40% have signed up.. But You can send bulletins out every few days to all of them to tell them about the site.