Warning: You should know, as useful as this extension is, the slimy developers decided it would be a good idea to auto post a recommendation of the extension to your G+ page the moment you install the extension – without your permission. It will do the same when you connect your twitter/Facebook too. The extension works beautifully but be prepared to delete the autoposts immediately after if you don’t want to spam your friends.
There are a number of extensions and tools out there that attempt to make it easier to cross post between Google+, Facebook and Twitter but perhaps none quite as flexible as Publish sync for Google+ & facebook.
The extension makes it possible to post from either Google+, Facebook, Twitter or Plurk and cross post to all (or just a selection) of the others. It unfortunately doesn’t support Facebook Fan Pages but does support crossposting to specific G+ Circles which is nifty – particularly without a public API.
It currently works seamlessly with text and links; video and images only work when cross posting from Google+. Grab it here. And for more quality Google+ resources check our Mother of All Google+ Resources Lists and this Tumblr.