Already in production. Connecting the 200 million or so Gmail users with Google+ is a logical product integration. Users have said they want to be able to post content to Google+ from Gmail as well as read comments that others leave on those posts from Gmail. Users also want to receive notifications of Gmail messages on their Google+ bar. There are a myriad of possibilities here.
A logical extension to Gmail integration is a tie-in across Google Apps, including Google Docs or Google Sites. Users may already provide comments for Google Docs. But imagine being able to tap into Circles from Docs and even spark Hangouts for video-chat sessions. The Huddle group-messaging application could also be integrated with the Google Docs mobile application for conversations on the go.
This is a no-brainer, particularly for consumers who like to watch entertaining videos together. Imagine posting a YouTube clip of a newborn baby and inviting friends to a Hangout to watch and comment on it.
Anyone up for being able to have Google+ streams sent to their Google Voice account? How about being able to access Google Voice messages—both audio and transcribed—from the + application. Users could then choose to share those messages with others in their Circles. Google integrated Voice into Gmail last summer. Surely, it could do the same for Google+
Some folks at Google will tell you reading and sharing news is a social event. If this is the case, why not allow users to receive popular Google News feeds in Google+, where users can share them with their Circles. Or why not offer Google+ comment streams right on Google News where the public can view comments?
This might seem a little on the fringe and unsteady, considering Offers is by no means a proven product with the staying power of the likes of Groupon or LivingSocial. But we could see Google+ integrated with Google Offers to let users share deals and comment on them. It would be akin to the integration that lets Groupon users share their purchases with their Facebook friends. Users would share deals with their Circles and discuss the merit and value of them. This could extend to mobile as well.
Another logical integration exists between Google+ and Google Maps. Users can share maps they like with folks in their Circles, and perhaps even leave comments on Google Maps for those in their Circles to see. Or users may "build" maps, comment on them and send them to users as a nifty resource. Heck, users can even do this via Hangouts to make this map-making a fun, collaborative exercise.
If Google is going to tuck Google+ into Maps and vice versa, it must extend this to Google Places, where users will be able to share their honey pot recommendations and other ratings and reviews with their Circles contacts. As with Maps, users should be able to comment from + right on Places local business listings.
Google Books, which launched last December with more than 3 million titles, is plodding along, compared to Amazon's Kindle bookstore and Apple's iBookstore. The company just unveiled the iRiver Story HD, the first e-reader integrated with the Google eBooks platform. Why not spruce up the service by enabling users to "share" digital books via Google+ and comment on them? It might help the service gain more traction.
We haven't heard a peep about the Google Music beta since it launched at Google I/O last month. We think a Google+ integration, where users share and comment on tunes from each other's Music libraries, would be a nice social promotion. Users could also Hangout and listen to music together.