Starting with 2005, VS started this behavior of when starting debugging session it spawns up a webserver for every project in a solution. I have a solution with 15 projects
I have also been highly annoyed by that behavior. The only solution I have found is to manually change the properties page for each web appllication so it hits a real running instance in IIS.
I prefer this anyway, because debugging with the integrated web server can give you a very false impression of how your application will interact with the IIS security model.