Now Google+ allows you to share your circles.
- Click on circles and go to the circles page.
- Click on the circle that you want to share.
- Click on the link "Share this circle" at the top right.
Though sharing your circles, seems to be a minor feature. It will have a great effect on growth of Google+ in the short and long terms.
In the short term, since Google+ has gone public all the newbies will find it really helpful. So if I have newly joined Google+ all I need to do is a find a circle of my interest that is shared by somebody and just add it to my circles. Bingo! like magic Google has solved the problem of empty stream in one go. What Google has is it has taken the smart way of crowd-sourcing the featured lists.
In long term what happens is people have a reward for discovering new people who are interesting, who share great content. A person who can share a great list of people to follow will definitely start garnering more followers. This will help Google to prune Google+ and more people will have more interesting guys to follow, which is great for the community.