How do you find neighbors online?

I launched CornerChamp.com today -- it's a game where you guess what neighborhood homes really sold for. My parents probably bought their home for too much; and I think crow-sourced estimate data could beat Zillow & Redfin's estimates, which would've helped my parents... But that data comes from users, I've got to find some local folks that are willing to estimate homes in their area for me.

How have y'all found local growth?