Pin Drop is a new iPhone app and website which helps people mark locations that matter to them. One or two other startups are trying out this arena, most notable Everplaces , still in private beta, however it feels like the market is wide open for this kind of application which you could also describe as a sort of Evernote for location I think. Users can drop their own pins or they can take inspiration from the curated lists feature. Each pin can then be assigned to multiple categories allowing users to build up a library of their favourite locations.