In the blog entry Listing all the COM automation PROGIDs http://blogs.msdn.com/powershell/archive/2006/06/29/650913.aspx . I showed how you could use the registry to get all the progids that you can use for COM automation.

Here is a way to do the same thing via WMI (which allows you to do it to remote machines):

Get-WMIObject Win32_ProgIDSpecification |
   Sort ProgID |
   Format-Table ProgID,Description -auto

Jeffrey Snover [MSFT]
Windows PowerShell Architect
Visit the Windows PowerShell Team blog at:    http://blogs.msdn.com/PowerShell
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PSMDTAG:FAQ:  COM Progids – How do I know which I can use (answer 2)?
PSMDTAG:FAQ: COM Progids – How can I see a description associated with them?
PSMDTAG:TYPE:COM: progids
PSMDTAG:TYPE:WMI: Win32_ProgIDSpecification