More precisely, you can share static snapshots of circles
Starting today you can actually share your favorite circles with others! So if you’ve got a great Photographers or Celebrities circle, for instance, then you can share a copy with your friends.
To get started, just click on a circle from your Circles page, and click Share.
(Importantly: when you share a circle, you’re only sharing its members at that time. Also: the circle name is always private to you, and any changes you make afterwards are private as well.)