Confidentiality, in light of Plamegate ... how far does it go?

Well, we know that journalists are not guaranteed confidentiality re: their sources at the federal level. But what about other professions, like lawyers or clergy? If a hypothetical White House leaker revealed the identity of an undercover CIA agent to his/her attorney, could that attorney be forced to testify before the grand jury? What about if the leaker revealed the same to his priest during confession … could the priest wind up on the stand?

Is there any difference here and in normal criminal proceedings? After all, in the case of a leak, the passage of the confidential information IS the crime itself–as compared to say, a confession to a priest that revealed incriminating details about a murder (where the murder was the crime, but talking to someone about it was not).