You've identified one of the more interesting parts of Google Plus in my opinion, actually, the ability to assemble a group or list (alright, or "Circle") of people and then share taht group with others. Sure Facebook has lists, but they've made those lists so difficult to work with that no-one I know uses them, and the idea of sharing a list? Not really how Facebook works, even with the ability to subscribe to users you don't have a "friend" relationship with.

I imagine you know how to "circle" someone on Google Plus, but if you don't, simply hover over their name on the service and a little window pops up with a "circle" button right there. That's easy! You can either circle them into a specific labeled circle (like "family") or you can drag and move them around after the fact by going to your Circles page.

I'll show you because it turns out that the Circles page is also where we need to go to share an existing circle.

So let's start there. On the left side of your G+ page, look for the "Circles" icon:

Click on it and you'll see a list of your circles half-way down the screen:

I'm going to share my Intel Corporation circle, so I'll click on that one. Now the top of the page changes to show me who is in that circle:

Meanwhile, on the bottom, I can move my cursor over the circle and a number of options appear:

As I've highlighted, you want to click on "Share circle", the middle option. Click on it and a big window pops up:

You can probably figure things from here, but I'll go through the rest of the steps anyway. Enter a useful and interesting comment, remembering that words surrounded by "*" become bold and words surrounded by "_" are shown in italics. Here's what I wrote:

I share it by clicking on "Share" and it's posted to my stream and that of anyone who has circled me on Google Plus. I know because a tiny confirmation appears at the top:

More interestingly, here's what everyone subsequently sees:

So now you know how to share a circle in Google Plus. Nice. Want to find me on Google Plus, btw? You can: Dave Taylor on Google Plus. Why not Circle me while you're at it? :-)