I would like to see more social networking and social graph management tools, like their recent social graph api release.
Now Google has added another simple, yet powerful tool to their API arsenal. A common contact list has helped power applications like Gmail, Google Reader, and Google Calendar, and with the launch of the Google Contacts Data API, you can access this list with other external applications.
Based on AtomPub, the Contacts API can be used to read, create, edit, and delete contact information stored with Google.
Learn the details from an announcement post on the Google Data APIs blog.