When it comes to map mashups there's no doubt that Google Maps leads the way. On ProgrammableWeb we list 1,964 Google Maps mashups, almost four times as many as any other API. This popularity makes utilities built on top of Google Maps especially interesting, such as this contextual menu control, which pops up a menu when the user right clicks.
The Wikilocation API has expanded to include 36 languages. The geo API for Wikipedia allows developers to find articles with subjects near a specific location. With the new languages, there are now over 3.8 million geocoded articles available via this unofficial API from developer Ben Dodson.
Foursquare has launched Places API for Start-Ups which provides access to Foursquare location intelligence capabilities at a price point between the free tier account and the Enterprise tier account. The Places API allows companies to integrate apps with Foursquare platform data and capabilities.