By all that data provided by profiles on social networks a new breed of applications and especially mobile applications are coming up with mobile being the place, where this special information about locations and localization is most useful.
Sonar is most interesting. The app aggregates and analyzes demographic and geographic data from social networks like Facebook, Foursquare and Twitter with the intention to deliver information on how many people interesting to the user of the app are within a location. Furthermore the app indentifies people within a location and is giving particular information to the user, who will be able to find someone to talk to. See also this review for some further information about Sonar.
The app SpotOn has a different intention, but is based on aggregated data in a similar way. The service is providing location based information about locations, but opposed to other recommendation services the app is providing personalized data e.g. based on favorites of friends. For more read this article and visit SpotOn.