Setting up sites using only an IP Addres

If I had an IIS server and I purchase a block of IP addresses from a local ISP as well as a dedicated Internet connection and I want to set up several of those IP addresses for websites without a domain name, how would I do this?

Basically, I want people to be able to go to the site using its IP address, but it won’t have a domain name registered for it. Would the ISP have to set up something from their end or would they only have to do this if I were using a domain name?