The SharePoint product team has released the first version of the Microsoft SharePoint Administration Toolkit which is supported on MOSS and WSS.  I was surprised that it didn't have that many initial tools- but the ones it does have are super sweet.  I think the feature that is going to be welcomed most by SharePoint admins is the ability to move a site collection to a new content database.  There are promises of future and regular releases so I can't wait to see what they add next.

Get all the details at the SharePoint team's blog: http://blogs.msdn.com/sharepoint/archive/2008/04/30/announcing-the-first-release-of-the-microsoft-sharepoint-administration-toolkit.aspx

Some tools I'd personally like to see in future releases (and to stay with the site collection theme here):

1. Manage multiple site collection themes - all or those selected at once (would just be nice to do this from CA instead of having to go to each site collection)
2. Manage quota templates for multiple site collections - all or those selected at once

- Dan Lewis