In this chapter, we talked about what third party mapping APIs are and how to use them. We learned how to use the Google, Yahoo!, and Microsoft mapping APIs, along with the OpenStreetMaps API. We also discussed Spherical Mercator and demonstrated how to use it. Finally, we created a map 'mashup', mixing various different layer types together.

The next chapter will focus on another part of OpenLayers—the Control class. This is another thing that sets OpenLayers apart from other mapping libraries. With it, we're able to interact with our map, add tons of additional functionality, and even create our own custom controls.