I think that you'll find this article a good read.
Google Plus doesn't have a public API
yet, nor has it announced when one
will be available. But if you want to
find out about future developer
opportunities, Google has a mailing
list you can sign-up for to receive
more information in the future.
There is an unofficial API, PHP.GooglePlusAPI, that you can use this to fetch public data. It's something to play around with while we're waiting for the full official API from Google:
Update:
I've just added support for feed posts as well. You can use this library in your server-side code to read a public profile, post, and relationship data, cache it in a MySQL database, and serve the data to a front-end as a JSON or JSONP service.