Here and onward in these days I am going to talk about Google APIs.

Google offers a variety of APIs, mostly web APIs for web developers. The APIs are based on popular Google consumer products, including Google Maps, Google Earth, AdSense, Adwords, Google Apps and YouTube.

Google Data APIs
The Google Data APIs allow programmers to create applications that read and write data from Google services. Currently, these include APIs for Google Apps, Google Analytics, Blogger, Google Base, Google Book Search, Google Calendar, Google Code Search, Google Spreadsheets, Google Notebook, and Picasa Web Albums.
AJAX APIs
Google's AJAX APIs let a developer implement rich, dynamic web sites entirely in JavaScript and HTML. A developer can create a map to a site, a dynamic search box, or download feeds with just a few lines of JavaScript.

Ads APIs

The AdSense and AdWords APIs, based on the SOAP data exchange standard, allow developers to integrate their own applications with these Google services. The AdSense API allows owners of web sites and blogs to manage AdSense sign-up, content and reporting, while the AdWords API gives AdWords customers programmatic access to their AdWords accounts and campaigns.