During my Office Development courses I always show the activated features on a Sharepoint web to the students.
This happens usually just after I explained how to install and activate a feature using the stsadm command tool. While explaining this I quite often make the mistake of type 'stsadm -o enumfeatures -url <myweburl>' which is a non-existing operation in WSS.
I was quite annoyed this option didn't exist and, since I wanted to check out the extensibility options for stsadm anyway, I decided to create this operation myself 🙂
If you like, you can download it here It gives you the possibility to display site- and web- activated features using the stsadm command tool.