You definitely need this tool if you are even serious about using SharePoint.
You can find it @ http://www.codeplex.com/spm
The SharePoint Manager 2007 is a SharePoint object model explorer. It enables you to browse every site on the local farm and view every property. It also enables you to change the properties (at your own risk). This is a very powerfull tool for developers that like to know what the SharePoint holds of secrets.
As a Sharepoint Administrator I am using this tool for getting a lot of information out of the farm that is not quite visible in Central Admin.
One of the coolest things I did with it was setting a Site collection to read only by just setting a simple dropdown box to the value true and wham the site is readonly! Try it out yourself.
It is slow on loading howevr, probably due to the fact that it needs to collect all that information first. So be a little patient when loading. Also it is a single executable file that does not require any additionale software installed on your MOSS / WSS servers