Getting terms for only one taxonomy from services module
I was working on exactly the same thing the other day, the format is like this:

http://domain.com/endpoint/taxonomy_term?parameters[vid]=2


To explain that a bit further...

If you look at the code in _taxonomy_resource_definition() the index resource defines a few arguments:


page (int)
fields (string)
parameters (array)
pagesize (int)


The way to pass any of those is:

http://domain.com/endpoint/taxonomy_term?arg_name=value


Since parameters is an array you need to format it as if it was an associative array in the URL, so you use (e.g.) parameters[vid]=2.

It will also work for other parameters, e.g. parameters[name]=TermName.