The Transit App, an application that provides commuters with real-time transit information on iOS, makes its Transit App API available to developers who may want to integrate the functionality with other applications. The app has already been widely downloaded and received positive customer reviews, and filling the gap that was left when Apple removed transit from its own Maps app, it seems to be a really useful tool for anyone who relies on public transportation and the ability to get accurate and timely travel information.
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.