Google has not released an official API yet, however, that does not mean you cannot start playing around with Google+ data.  There are quite a few unofficial API’s.  Here is a list I saw on ‘programmableWeb‘

• Google+Tweet: A full featured Twitter client inside your Google Plus Account.
• Google+Facebook: A browser extension that lets you view your Facebook stream inside Google Plus. It also allows you to Post to Facebook. Image above from ReadWriteWeb’s coverage
• CircleCount: A web application that takes a Google Plus profile and counts the number of followers and friends.
• PHP-based Google Plus API: This API provides public user and relationship data in Google Plus. It also allows to post to a users activity stream.
• Rudimentary Google Plus API: A Read Only JSON API that accepts a Google Plus profile id and gives you profile information and posts. The author, Emlyn O’Regan has also written a tool, Syyncc for tying together various social networks and currently supports extracting out data from Google Plus to other Social networks.
• Google Plus – Share to Twitter/Facebook : A Chrome browser extension that allows you to share your Google Plus posts to Twitter and Facebook.

I’ve decided to download one from