It's tempting for the worship committee (or like) of small congregations without a regular preacher to act like talent scout for a lyceum series. (I've seen this among non-Unitarian Universalists, too.) If all else fails, the "sermon slot" must be filled. A small drama or pagent, poetry reading, panel discussion, or special music event can be slotted in from time to time, but the place it fills is the sermon slot. If the Sunday service has an identifying description, nearly all of the time it will be the title of the sermon. It has become the heart of what's done on Sunday morning. Wrangling willing speakers -- if my experience on the other side of the equasion is any indication -- is a difficult and thankless task. Even worse, the quality suffers, and the variety (which could be high) tends to boil to "my impression of this important thing" and "this is why Unitarian Universalists are different than X."
There ought to be a better way.
Most -- since this includes the Catholics -- Christian churches use a church calendar, a duplex arrangment where (1) the life of Christ, centered on Easter, is played out in one- and three-year cycles, with (2) the lives of the saints and other commemorations peppered in, the so-called sanctoral cycle. Some "sermon centrality" has been softened by relying on the themes that draw naturally from the church calendar. These so-called lectionary sermons -- even the so-so ones -- receive reinforcement from the matching hymns, prayers, and the lessons themselves. Sure, topical preachers usually craft a service with these features, but it is much harder. And this doesn't even consider the sensibilities of those who really don't care about the sermon, and get their sustainance from non-spoken cues.
So how does this relate to the non-Christian congregations? Perhaps they should develop a church worship calendar. But it would out of necessity be an amplified sanctoral cycle (which we do: Martin Luther King Day, United Nations Day, and forth) based on the seasons, or likely a combination of the two.
If I -- and in practice, this ought to be a group effort -- were setting up such a calendar, I would make a chart of every day of the year, and highlight the Sundays. Then I'd add in the special days that the congregation values, and transfer the fixed dates to the nearest Sundays. I'd then try to identify them with words that express values: truthfulness, mercy, hope, integrity, and the like. That might fill in a quarter or half of the Sundays.
Now I'd bring in a clue from series preachers. A series of related themes have a synchonicity that isolated themes can't generate, but the series should run from three to five weeks. I'd identify overarching themes that can center on (or bridge) the special dates/themes already decided. One comes to mind: United Nations Day (October 24) makes me think of international unity, while All Souls Day (November 2) reminds me of the unity between the living and the dead. I'd try to flesh out a series of three to five weeks that expressed other themes of human unity, for example. If you can build up to a thematic climax, so much the better. Complete the year, knowing that a few stand-alone services will probably pop up.
Now here comes the hard part. I'd write a declarative theme for each Sunday, but with a good verbal rhythm. Lines from hymns might be a good choice, and I'd make that the "title" for the service, if one is required. And more about that declarative theme next time.
But here's the kicker: get speakers or sermon-slot elements to match the theme. With the themes known so far in advance, I think it would be easier to people to look forward and select a theme than just filling time that yawns threateningly.