Buddhism - usually of the Mahayana tradition - is the dominant religion throughout the system, particularly on the Central Planets. Christianity ranks second, with larger concentrations on the outer worlds, as Christians migrated away from the centers of Buddhism. Most Christians in the 'Verse follow a Protestant tradition hailing back to Earth-That-Was. Catholicism still exists, though the exodus of long ago ended its original structure.
One group of Christian missionaries, the Order of Shepherds, still follows the monastic tradition. These men and women take vows of poverty and chastity similar to those of a priest or monk of old. They may live and work in an abbey or travel the Black to find a flock in need of a Shepherd. Their peaceful order is generally respected throughout the system. Shepherds look to Christian scripture as their faith's grounding. They do not claim to have all the answers, but are here to help spread the word to those that need it told to.
There are many other religious groups in the 'Verse, including Muslims, Jews, and Hindus, who tend to form their own communities where they can worship in a body, follow their own traditions, and bring up their children in their own culture.
Out on the Rim, one can find any number of faith healers and wandering preachers who have founded their own churches or, in some instances, established entire communities. Some of these people are well-meaning and do lots of good, but others are swindlers, who use what they call religion to bilk the innocent out of their hard earned money.