Before it become apparent that google+ was a veritable ghost town, I thought that the concept of circles was a pretty neat idea. Rather than take the Facebook approach and make your post visible to everyone, you were encouraged to kind of whitelist your post to relevant circles (though you could still scream out into the wilderness if you wanted).
Recently, I became curious if the same feature was available on Facebook and, wouldn’t you know it, it totally is. Anytime you post something there is a drop down list that says ‘public’ by default. From here you can narrow the scope of how visible your posts are. The real power of this feature is the ‘custom’ option paired with the way facebook encourages you to organize your friends into different lists, which you have the option to do anytime you view a friend’s profile. Once you have your list organized the way you want it, you can post exclusively to that group, or exclusively exclude them.