G+ Count Favicon
Replaces the favicon on plus.google.com with one that shows the current notification count. Trivial but nice visual notification.
Replies and more for Google+
Adds reply and reply-to-author buttons to Google+ comments and Share dropdown menu with options to share a post on Twitter, Facebook, etc.
Google+ integration for Chrome. Harnesses native Notification component. Allows to reply without the need to open G+ page. Doesn’t allow +1 posts, though. Extremely useful for quick replies.