Five APIs that developers should know about

Developers have arguably never had it better. A big reason for that:
there are virtually countless APIs that enable developers to build
really cool applications on top of foundations that someone else
invested in laying down.

When it comes to APIs, however, a lot of attention is focused on
popular services that have created platforms that developers can tap in
to. Facebook and Twitter are two of the most prominent, and many developers have cashed in developing on their platforms.