You need to set up apache to use virtual hosts. Not too sure how to do it, as I've never tried, but there's a (brief) introductory explanation in the book "Linux: Network Solutions for your Office" by Viktor Toth (published by Sams, I believe), by checking in the www.apache.org
web site (again, look for Virtual Hosts references) or by searching on Google.
Virtual Hosts let you bind multiple IP addresses to a single NIC--pretty cool. Then apache can display the appropriate default web page based upon the IP address of the incoming requests. WAY cool!