I am interested in a career in medical transcription.  I have no
training in the field, so I would like to know which are the most
reputable institutes that I should consider studying with.  I would
like to do my studies online, and I live in Canada.  I would also like
to know if there is any standardized diploma in this field.  I would
also like to know the real scoop on career opportunities from someone
who is in this field or knows someone in the field - how much money
can I expect to make, and if I only want to work from home can I
expect to be consistently employed?

There are 2 schools currently approved by AAMT - Andrews and MTEC. 
CareerStep is also highly regarded by many and several national
companies work closely with this school.  There is no diploma, per se,
but one can take a certification exam through AAMT after 2 years of
acute care experience.

I think you can find answers to most of your questions by visiting
http://www.mtchat.com/ubbthreads/ubbthreads.php?Cat=

There are several "pinned" topics in the New MT forum that give tons
of information, and once you've browsed through the information and
previous discussions, you'll be better prepared to ask more specific
questions.