Foursquare is a location-based social network with gaming elements, and it is the latest hype among tech savvy social media users. Its mobile app lets you check-in at different venues and find out where your friends are. Today the site added 15 new European cities (not 14 as published on TechCrunch) to the two existing, London and Amsterdam. Stockholm is one of the new cities that is available as of today. The other cities are Athens, Barcelona, Berlin, Brussels, Copenhagen, Dublin, Helsinki, Geneva, Madrid, Munich, Manchester, Paris, Prague and Rome.