Yes, there are atheists and agnostics who want to gather with others on Sunday morning.  At the Unitarian Univesalist Church, worship language is open enough to include them, along with others who are less reluctant about the holy.  Something happens, these unbelievers will say, when they gather with others, a sense of presence beyond words, an opening to the mystery beyond human understanding, sometimes a glimpse of the unity of all that is. From being together on Sunday morning, they draw inspiration, hope, and courage to meet life's challenges.

There are those who say that "worship" is a transitive verb, that there must be an object, a "something" that is worshiped. The ancient roots of this word, "worship" are about honoring what is "of worth". In response to this idea, an atheist might say that to reduce that cosmic worthiness to a mere object seems arrogant.  To leave the door open to what is beyond words makes more sense.  It's true that the God many atheists don't believe in is the same God that you don't believe in -- the grumpy old white man with a beard, sitting on a throne in the clouds and making judgments on people's affairs.  When pressed, an atheist may say there's "something out there" beyond our science and reason, something with power and glory, something unnamable. Maybe they believe it is ultimately knowable, and certainly not outside Nature, therefore not "supernatural," but worthy of attention with our limited knowledge, especially worthy of investigation..

This line of thought can lead to noticing that the same sense of a powerful mystery beyond our daily understanding appears in the great faiths of the world, an unnamed presence with many names, something of worth that is sought in many cultures.  An appreciation of what is universal across the world's faith traditions is part of our practice in Unitarian Universalism.  Some seekers in our tradition will discover this and begin to say "God", for want of a better word.  Others continue without naming, opening themselves in worship without saying they worship anything or anyone. It's not a bad thing to leave it nameless.  Nor is it a bad thing to ask of  worship that it engage the thinking part of the human being.  Indeed, it's not bad if a community of worshipers expects to be taught about the holy through individual experience and reflection, rather than through doctrine.

So it's true, there can be worship without God, a worship that can be deep and meaningful, a source of guidance for life, and a source of hope for the healing of the world.