1. Start a facebook, linkedin, friendfeed, or ning group about your passion. Collect everything that’s ever been mentioned about it. When people want to know anything about your topic, you’ll be the top Google result.
2. Write about your interest on a blog. Alert other enthusiasts to the fact that you are doing so.
3. Reserve a booth at your subculture’s convention. If there is not yet a convention for it, start one. Or at least a Meetup group.
4. If you have a bizarre opinion or accomplishment in your niche, publicize it. Become known as a spokesperson for everyone who believes the same as you.