I have looked at the Microsoft instructions for customizing the drop
down menus and other items using the ONET.xml file.
(msdn.microsoft.com/.../en-
us/spptsdk/html/tsptAddingContextMenu.asp) This involves adding
another javascript file to the template to override the default and
is accomplished by the tag below:

<Project Title="Team Web Site" ListDir="Lists" xmlns:ows="Microsoft
SharePoint" CustomJSUrl="/_layouts/[%
=System.Threading.Thread.CurrentThread.CurrentUICulture.LCID%]/custom_
ows.js">

My problem is that I don't know which site definition to modify.

The instructions state to find the file in the path that corresponds
to your site definition. There are a number of folders in there with
names like SPS, STS, SPSSITES, SPSNHOME, etc. etc.

I have made WSS sites using the team template and the document
template. Which site definition are these using? I have tried
changing 3-4 of them and cannot get the change to show up unless I
modify the ows.js file directly. (Yes, I have restarted IIS after
each XML change and tried making a new site).

Any idea where these are documented and how to get the change to
apply to a site?