Google continues to push away at improving its platform-as-a-service offering, the Google App Engine API. It has already seen two minor releases this year with the latest release bringing in much needed updates to the XMPP and Task Queue APIs. An earlier release in the year focused on the High Replication Datastore, that was clearly targeted to mission critical applications.
There is something to be said for simplicity, especially when it comes to applications that leverage web APIs for mobile devices. Enter Sparrow, an application for the iPhone, that serves as a good example of how a few web APIs can be elegantly implemented for use on a mobile device.