I like this one for several reasons:
http://www.craftlister.com/
It will list fairs by distance from your zip code
It will email you with new listings if you want
It's free
Very complete information regarding each event, including
anticipated/past foot traffic.
You are competing against established sites, there are other
subscription sites as well. Could be the market is saturated or people
won't pay for info that is otherwise available for free.