I'm doing some work with Microsoft Office SharePoint Server (MOSS) and I recently discovered that with MOSS (and WSS v3) the administration utility is extensible. Stsadm.exe is something that I have a love-hate relationship with, but it's interesting that it's commands work on a provider model. Tony Bierman has posted all the details on the SharePoint Solutions Blog and Andrew Connell has some real-world examples of custom commands.
I can see these custom commands being really useful in many MOSS deployment scenarios - anyone who has ever tried to write an MSI or a batch file deployment for a SharePoint site will know how invaluable stsadm.exe really is. Of course it does raise a bootstrapping issue, in that you have to get your custom commands deployed before you can use them for the rest of your deployment. However, this shouldn't be an insurmountable problem.