adam hoyle presents suckmypixel

CloudMade help you make the most of map data. We source our maps from OpenStreetMap, the community mapping project which is making a free map of the world. Our aims are to continue the democratization of geo data and to expand access to open geo data through a range of simple yet powerful tools and APIs.

Not public yet, but another map provider making an iPhone maps API

A slippy map library for the iPhone.
Fast! Completely written in objective-c using CoreAnimation. Runs like the built-in app.
Currently OpenStreetMap Microsoft VirtualEarth and CloudMade are supported as map sources.

A component that you can add to your iPhone application to access all basic features of Google Maps (similar to Android's MapView). It uses a UIWebView in the background to load the HTML/Javascript version of Google Maps, and offers a set of Objective-C methods that mimic a subset of the original Javascript methods for controlling the map. It currently supports setting the center location, and zooming & panning using the touch interface.

The Google Data APIs Objective-C Client Library provides a Mac OS X framework and source code that make it easy to access data through Google Data APIs.

Not sure if this library will support iPhone or not.

VirtualEarthKit is a framework to allow Cocoa developers to communicate with Microsoft Virtual Earth. Microsoft Virtual Earth provides a wide range of services, including geocoding, reverse geocoding, map imagery, route guidance, and business lookup.