Someone has already set up;

"BestIn.com" sites.

"BestInAtlanta.com"...."BestInMiami.com"...."BestI n____.com"...etc (Hundreds of Domains)

They sell these sites and the person who buys a "Directory" site can then put Categories in the Directory;
"BestDentistInAtlanta.com"..."BestCarpetCleanerInM iami.com"...etc

Don't know how they're doing but, sounds like a good idea to me.

Don Alm