If you've spent some quality time with Google+, we're sure you've encountered Circles. You know, the feature that enables you to control who sees your G+ posts and who doesn't. Now, the folks in Mountain View have added the social network management tool to Google Voice. You can organize your contacts into groups who can actually ring your Galaxy Nexus and those who are sent straight to voicemail. Custom greetings can also be added to each Circle, should you feel the need to offer some Punch Brothers instead of the boring ol' standard ringback. Looking to take 'er for a spin? Hit the Groups & Circles tab in your Voice settings in order to customize your sets of contacts, but take note that your existing Google+ Circles are getting cozy there already.