Search for local networking groups, Meetups, and service organizations where you can connect with others. Whereas the majority of these people will not be directly interested in your specific topic, they will most likely know someone else who is. Often times a personal recommendation goes a lot further than a virtual introduction does.
Now that social media is front and center, make sure that you have spent some time on each of the major players in this arena, including LinkedIn, Twitter, Google+, Facebook, and YouTube. I highly recommend branding your name with each of these, enabling your profiles to be found on page one when someone Googles you.