I would say that CNM's generally make more money than LM's, CPM's, etc. As was previously written, CNM's tend to work in hospitals, often in partnership with OB/GYN's, some in freestanding birthing centers, CPM's/LM's tend to work in freestanding birthing centers or homebirth settings. CNM's can offer well-woman care (PAP, STD exams, etc.) and sometimes are trained in some other office procedures as well. *Some* CNM's are more "medicalized" than CPM's/LM's (as opposed to a more "natural' birth model of care, for example frequently using Pitocin for induction/augmentation, etc. etc., *some* CPM's/LM's are more "earthy-birthy"- these are generalizations, I am just reporting the differences or often *percieved* differences as I often read, I am not there yet so this isn't my opinion. Obviously everyone is an individual and there is a broad spectrum of beliefs and practices).
CPM's (they are non-nurses) take the NARM exam:
http://narm.org/
MEAC accredits programs for CPM's:
http://www.meacschools.org/
MEAC approved schools for CPM's:
http://www.meacschools.org/programs/programs.html
CNM's (they are RN nurses who go to grad school for CNM) take a board exam through ACNM:
http://acnm.org/
The ACNM midwifery education page:
http://www.midwife.org/edu/
ACNM approved schools:
http://www.midwife.org/edu/schools.cfm
HTH