Create site collections by Host Header.
You can not create host-header site collections on Central Admin with SharePoint 2010, out of the box. For those who frequently need to create sites collections by domain, can install and use this as additional tooling from Central Admin.
Note: This is a Farm solution for SharePoint 2010 only. It has now been tested for working on RTM. Please ensure that you are running Central Admin as Administrator on a Vista/Win7 UAC environment. I have noticed issue in "deploying" the solution when IE is not running as Admin. Once a site-collection is created, its binding should be present in IIS pointing to relevant SharePoint web-app.
I have set this as Beta for now, in case any issues are reported that I haven't come across.