Do you have an interest in crochet? Extreme ironing? Wearing only green shoes? There is probably a social networking community out there for you so you can connect with like-minded people who share your interests. At SMX Social Media this afternoon Rand Fishkin and Liana Evans both spoke on how to find, use and leverage these smaller social networking communities.
To find these micro communities in your vertical, you can check out the web 2.0 lists of social media lists, search for topic relevance and coverage in a search engine and read the social media discovery blogs. The long tail of social networking sites and micro communities is very, very long. You will be able to find a targeted micro community focused on what your interest is.