Mike Mosey is his Rackspace Cloud Blog post http://www.rackspacecloud.com/blog/2010/08/23/running-multiple-websites-on-a-cloud-server-with-1-ip/ addressed how to run multiple Websites on an Apache server. What if you are running IIS7 on a Windows server? Well - yes you can - easily run multiple websites on one IP using Host Headers (bindings in IIS). In this brief post, I'll describe how to set it up in IIS. The Rackspace Windows Cloud Servers just came out of Beta. As an initial Beta customer I was extremely impressed with how easy it was to setup and provision a Windows server. Launch Windows Servers on the Cloud in Minutes.
To get started, learn more about Cloud Computing & Hosting from Rackspace. After your server is provisioned as a website, follow the directions in Rackspace's knowledgebase to setup your DNS A an
d CNAME records for each website's domain. Then in IIS, simply create your websites and assign the domains in the bindings for each site.

Good luck and Happy Hosting!
Don