In this blog Making certain volunteers feel unwelcomed because of your language, the blogger explores the issue of religious volunteers in a group that doesn't officially identify with a religion making other volunteers feel unwelcomed. The example used is a Facebook group that is supposedly for all volunteer firefighters. In response to the religious message, which is meant to inspire, the blogger asks:
"Can you imagine if the administrators posted a message that assumed all volunteer firefighters are atheists and, if they aren’t, they should be? If a message was posted saying that the best way to handle challenging situations in life was to NOT believe in a god? Can you understand how that kind of message would be completely inappropriate for a group for all volunteer firefighters, not just religious ones?"
And speaking of volunteering, here is a list of Group Volunteering Suggestions for Atheist and Secular Volunteers - places where you will be welcomed with your time and expertise to help others!