AWESOME tool for SharePoint developer just like .NET Reflector for .Net developer.
SharePoint Manager 2007
from the same guy who wrote WSPBuilder (another must have tool.. I think)
Words are not enough to describe how amazing this tool is. Go download it now! And you will addict to it.
Finally....we can all stop writing console app just for checking SharePoint Object Model properties. (well.. in most cases)
Download counts for this tool is surprisingly still low (1106 downloads at 16-April-08). That's one of the reasons I post it here to spread word :)
Here are some screenshots
View every Solutions installed on server..
View Lists, Lists Definition or even in Browser view..
View List Schema..