There are several cases in which it might make sense to tailor your app's content based on a user's physical location. But asking them directly is a bit of a pain. Luckily, it's extremely simple to find a user's location knowing only something you will always know about a visitor: their IP address. Today I'll walk you through how to use IPs to geolocate your visitors in a Rails application using Geokit and MongoDB's geospatial indexing with MongoMapper.
via NoSQL databases