Recently I noticed a few people asking for assistance when Hosting multiple web sites but do not have the luxury of owning a dedicated C-Class subnet... Hopefully these articles can get you going quicker if you do come across this question.
Hosting Multiple Web Sites (IIS 5.0)http://support.microsoft.com/default.aspx?scid=kb;EN-US;q190008
Hosting Multiple Web Sites (IIS 6.0)http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/e7a21b1f-ab13-47f2-8c61-b09cf14a7cb3.mspx
Configuring SSL Host Headers (IIS 6.0)http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/596b9108-b1a7-494d-885d-f8941b07554c.mspx