The first thing that comes to mind is "band", or "company". You could refer to such a group figuratively as a militia, using the word to indicate the marching aspect even if the group isn't military.
A group of similar individuals living together in an area is called population.
When a group of people get together to make a quilt together, this is called a quilting bee. When a group of people get together to share, sell and buy quilts and information about quilting, it is called a quilt show.
Quartet.
teamwork/ partnership
A gang of people
A group of six people is a sextet. A group of six babies born together is sextuplets.
dancing,marching or swimming.
the group of people forming a community that interacts together is called society.
it is a group of bad people[;
A Commune
Any group of people working together to improve the health of an individual or group are a medical team.
A group of Tigers that live together are called a pack.