I know I've read it somewhere, but what are the normal and special ranks/titles for priests in the church?

The Lexicanum wiki lists the following

The Ecclesiarchy is not part of the Adeptus Terra , but a wholly separate organisation. At its head is the Ecclesiarch , who, by tradition, is always one of the High Lords of Terra . Below him are the Cardinals , of whom there are several thousand. Below the Cardinals are the Ministorum Priests : Deacons , Pontifices , Confessors , Missionaries and Preachers . Other specialist ranks and duties include Cenobites , Relic-Keepers , and Chapel-Masters .

Also note that there appear to be several 'tiers' of Cardinal - some are referred to when given their full title as 'Cardinal-Astral' - they're the ones with planetary or more-than-planetary dioceses, whilst a 'normal' cardinal might be the ecclesiarchal head of a hive city.

Deacons are priests but often priest-administrator or aids to someone superior, running the Ecclesiarchy's 'civil service' - a good example is Mammon, who's more or less directly responsible for the Vraks war.