In reply to daniel baker: When you say mountain guide what EXACTLY do you mean? The term is used differently in different countries and by different people.
A Mountain Guide, is a fully qualified Mountaineering professional who has a many years of experience and has to achieve some minimum standards in any member country of the IFMGA. These folks are the top level qualified professional but it takes many many years and quite a bit of cash to reach this level.
A mountain guide (note no capital letters) can be a person who holds a recgonised qualification or experience level in the mountain environments. Again different qualifications in different countries.
There are only a few countries where you are legally required to hold a full Guide carnet, eg it is not required to hold one to work in the Greater Ranges!
Have a good look around and check out the links already posted, as well as www.mlta.co.uk.
What is your current experience level? Where do you want to work? etc