+David Yong-Mallo has some great suggestions for other uses of your Circles:
"Circles are useful for more than just sharing with others
I have a "Read later" circle and a "Drafts" circle, both of which include only myself.
When I see a post I want to read later, I share it only with my "Read later" circle. Then when I have some time, I open that circle and read through (and delete) the saved posts.
When I have an idea for a post, but no time to write it, I draft a rough version and share it with my "Drafts" circle. I can edit the draft by using "Edit this post" from the dropdown menu. When the post is complete, I just copy it to a new post that I can then share to my circles, after which I delete the draft post.
You can easily extend these ideas to collaborative sharing and editing."
What have you used Circles for?