Very helpful: http://blogs.iis.net/jeonghwan/archive/2008/07/30/iis-powershell-user-guide-comparing-representative-iis-ui-tasks.aspx
Check section 17, case 2:
new-webbinding -site foo -ipaddress * -port 80 -hostheader bar
If you create a iis.csv file like this:
site,port,ipaddress,hostheader
"default web site",80,"*","abc"
"default web site",80,"*","def"
You can simply do:
import-csv iis.csv|new-webbinding
That's it!
[Update: Now, this is assuming you're considering using the new IIS PowerShell snap-in. It is still in a preview state.]