How can I get users to my Sharepoint portal without having to authenticate via Active Directory?

We have a Sharepoint portal that we are getting to publish to the Internet. Currently, the site is up and running and internal users can access the site fine, where they will then log in through the portal (using SQL authentication) and it functions properly. We built an ISA server to accomodate incoming traffic from the outside, and this is where we're running into an issue. Users can get to the site externally, however, they are being prompted to provide Active Directory credentials before they can even get to the site. Is there a way to get around this? The portal will be used primarily for outside users, and we do not want them having AD accounts...instead, we want the site to appear as it does internally, using the SQL-based login.

Any suggestions?