Wildcards in domains / Apache setup

I have over 20 (and counting) domains running on our webserver (Server 10.1). I would like to be able to use wildcards in the domain names to allow both "domainname.com" and "www.domainname.com" without resorting to adding two posts to the sites list in the Server admin for each domain. I tested this out using both blanks and "*" without sucess. Any tips?