Collective noun for group of religious people

If they are Christian you can say the church. If they are not necessarily Christian you might say 'the faithfull' or, a following. There may be other better words, but I can't think of any right now. I will keep thinking.
If they have assembled for the purpose of worship, it's a congregation. You could also say an assembly, but an assembly is not specifically for worship.
Hmmmmm, there

a very interesting interesting topic... i have heard "flock" as a biblical reference to sheep (followers of jesus). for catholics, one speaks collectively of the "parishoners". the "faithful" (one "L") is another very general term. it depends on how big the collectivity is... for other religions, i look forward to reading!

Community?
Sikh community, Muslim community. Christian community.
Interesting: Muslims call Jews and Christians 'People of the Book'

http://en.wikipedia.org/wiki/Hermit

observance

Monks – abomination, cloister, or brethren while a group of monks living together are known as a monastery.
Mass of priests
skulk of friars
superfluity of nuns

congregation

Assembly

Congregation.... Is the answer

Congregants

collective form of religious people