Small forums believe it or not.

I own and operate a fresh new forum and from there, over the past month or so there have been 4 new clients sign-up for a hosting package from my company. Not because I'm the forum owner, or because the site design is cool....It's because I'm a part of the community.

If you can break into that lock then you should do quite well, once you have your shared client base then you're set to go into the full on banner and SEO marketing spree. Without people to back up your services (no matter what services they are) you won't succeed.