Let Users that are not part of domain access secure website

I am creating a web site for the company that I work for. We have a Windows 2000 Server running with AD and Exchange 2000. Now I want to give some of the people that are not part of our company access to our web site. How can I do it? How can I set them up? I tried set those people as contacts, but I can't set passwords on contacts, so they can use it to accsess web site. I then tried to set them up as a regular users, BUT since those people are not part of our company I don't want to give them our e-mail addresses. I know I can set up the user without setting him/her up on exchange, but then again I want to be able to see that person's OWN e-mail address when I try to send him/her e-mail.

Can anybody help?