If you are familiar with IIS, you probably know it was not possible to combine SSL with host headers. You could not have two or more web sites on the same IP address and port 443 and differentiate between them with host headers. For Sharepoint, that is a problem because it is not supported to bind a Sharepoint extended web site to an IP address explicitly.

Well, it seems there is a solution in IIS 6 on Windows 2003 SP1. There is a catch though: you will have to use wildcard certificates. A wildcard certificate is a certificate for a name like *.baeke.info. Not all CA’s issue this kind of certificate.

More info: SSL Relief for SharePoint