This is the article from Microsoft that I used on how to create virtual directories for OWA (outlook web access).
http://technet.microsoft.com/en-us/library/bb124811.aspx
http://technet.microsoft.com/en-us/library/bb123752.aspx
These are the commands that I found useful:
New-OWAVirtualDirectory -OwaVersion:Exchange2003or2000 -VirtualDirectoryType Mailboxes -Name "exchange" -WebSiteName "Contoso.com"
New-OWAVirtualDirectory -OwaVersion:Exchange2003or2000 -VirtualDirectoryType PublicFolders -Name "public" -WebSiteName "Contoso.com"
New-OWAVirtualDirectory -OwaVersion:Exchange2003or2000 -VirtualDirectoryType Exchweb -Name "exchweb" -WebSiteName "Contoso.com"
Written by Tom
