You can setup different authentication provider by zone on each web application.
Here is an exsulant overview of setting up multi authentication providers. Its an MSDN blog post which should be most helpful.
http://blogs.msdn.com/b/brporter/archive/2010/05/10/temp.aspx
Good luck,
Gary
Gary Newman MCSE, MCT, CCNA MCDBA, MCAD, MCSA MCTS SharePoint 2007 Dev & Admin MCPD SharePoint 2010 Development