How to show a list of users based on taxonomy?
First a little clarification of term meanings.  Taxonomy is a module that manages groups of terms gathered in Vocabularies.  You have probably created a vocabulary with the terms you listed in it.

To make your list you will use Views.  I am using D7 and V3, so I cannot give you a button by button instructions, but they are similar. 


Add a new view.  
Define the settings for fields and add a field for the User:name.  To do this in D7 you must add a relationship to the content author to expose the User Name field.  I don't think this is needed in D6.
Delete the node title field.
Set the path to a unique URL such as Group-Type/%/users.
Create an argument to filter the URL input '%' by a taxonomy term ID based upon the vocabulary you are using for the selection terms. 


When you enter a URL such as Group-type/stocks/users, The view should be used to generate a list of Users with that term.  

A cautionary thought:  I have not used D6 version of Views so I don't know its idiosyncrasies.  You may have to use the term id (tid) for 'stocks' since Drupal has changed a URL from an alias to a tid by the time the URL is passed to the argument section of the module.