for abbreviations:
http://www.biotechshares.com.au/MedLexicon.php

for words and phrases (note that you can use the wild card character (*) for any part of the word or phrase that you don't understand. You don't have to use quotes as you do in a Google search with a wild card)
http://www.onelook.com/

for almost any medical term or expression, especially ones that will get you questionable sites on regular Google
http://scholar.google.ca/
It turns up mostly abstracts of articles, but a lot of the time the information you're looking for is in the title

Lots of links for many things, including the FDA sites:
http://adminsupportservices.com/mojoslinks/links/

for doctors in Ontario:
http://www.ontariodoctordirectory.ca/index.html

for information on diseases, conditions, tests, and treatments:
http://www.fpnotebook.com/

Thank you so much cmt - great sites. Love collecting links to resource sites like these. Sharing some of my indispensable resources as well. Here are the links to some of them.

For word lists and phrase lists, as well as sample reports:

MT word help

For various types of sample reports:

MT samples

Nice dictionary!!

http://www.thefreedictionary.com/

Acronym finder - for all types of acronyms:

http://www.acronymfinder.com/

Search engine that searches just medical/MT websites:

MT word seeker

I haven't been able to get on for some time but tried to thank you cmt earlier, and thank you Barbara.

Well. I was just going to post that I stumbled onto a website that I think is real good: http://www.medilexicon.com/
It has done real well for me with abbreviations especially. But I have not seen it referenced here on the gab, which made me think that either everyone already knows of it, or I am too easily impressed. But now I see Carol T has listed it above (with a biotechshares route). Great. Maybe I am not too easily impressed! Or, well...