How do you promote volunteer stuff?

I facilitate a book group that I absolutely love! It's based on the concepts from Tim Sanders' Love is the Killer App. In fact, it was founded by someone who had just read the book. We each whatever we want to read, then come to the group and tell everybody about it. We have fascinating discussions, and leave with a list of what we want to read next (or what we should avoid).

It's rewarding, it's a tremendous source of information. And the group is down to four people. When they all show up.

We had a few dozen members when the group first started. That was years ago, and obviously time has passed, and people have come and gone (even some who seemed really committed to it). And those of us who are left kind of take for granted that it'll be there next month, so if it's not completely convenient, it's okay to skip it. After that…well, we'll see. And so we dwindle.

Now I'm going to spend some time promoting the group, trying to build it back up. The question is how?

Besides the cost to my business to spend too much time on other matters (see all those posts about Oktoberfest), I guess the real deciding factor for how much effort I should put into this is how much I get out of it. Okay, got that.

But what does one do—what do you do—to promote things that don't make money? If it's your kid's band candy sales, you offer it to the people around you at work. If it's a community service group, you might depend on the mechanisms already in place reaching the people who are used to supporting it—the Rotary Club website, the school bulletin, the local paper's Community Calendar.

What else do you do? How far do you go with business development techniques when what you're promoting isn't a business?

No, really. I'm asking.