You will need to use the Lists.asmx Web Service (can it be used with
Listings?) or write a custom Web Part.

We have the exact same set up on our company's faculty portal  --- one
is a private faculty only portal and the other is a public facing,
anonymous access portal. We wanted to display  the news items  from one
portal to another so that content managers would only work with ONE
list in ONE portal and content would automatically surface on the
second.

We used Web Services DataViews from a Custom List (and I think it can
only be done from list items) we created for our newsletter for this
functionality and I am still trying to work out some kinks, such as
calendar fields not working right in the filter options, but other
than that I was able to get it working. You will have to research some
and learn how to do Web Services DataViews --- its a bit more
complicated than regular DataViews and sometimes you have to add
little snippets of code here and there to make it work.

I have to say that this user group has been instrumental in getting
information on this and ideas and suggestions. I am sure folks here
will be glad to help!

I too have used DVWP's and the Lists.aspx Web Service to accomplish this kind of
cross Virtual Server presentation.

Does anyone have a good reference for me in using Web Services
Dataviews and how to show list items  from one SharePoint site to
another? I noticed that in this specific post they were trying to do
listing across portals; I just want to include a links list from my
top site on my subsites. Is this possible w/o using WSDV?

I am new to ASP.Net and SharePoint coding.

You don't even have to use the Lists.asmx Web Service. You can do this
within a Site Collection using SPD to create a Data View Web Part direct
to the list.