The MAPS.ME iOS API allows developers to integrate offline maps into their iOS applications written in Objective-C. MAPS.ME's maps cover all cities in all countries. These maps are highly detailed and zoom in and out smoothly.
Web and iPhone maps provider CloudMade can add a few more platforms to that list. Today it acquired German geospatial company One Step Ahead to incorporate Android, MeeGo and other mobile platforms to its suite of developer tools. CloudMade will also incorporate One Step Ahead's offline/online map technology, which passes a few map updates at a time.
New York City is probably best known for its skyscrapers and millions of people, not the trees that line its avenues. A new iPhone app goes out on a limb to give a little credit to the oaks and maples. And it's doing it thanks to open government data.