Google launched a new share button for their Google+ platform yesterday. They also made available an official bookmarklet which we frankly missed out!
You can get it here.
You just have to drag it to a toolbar in your browser and then you can easily share any webpage you have open on the Google+ network even if it does not have the share button.
Of course, if you are using the Google +1 browser extension in Chrome, you can already use it to share your current web page.