SharePoint Spy by Echo Technology
SharePoint Spy is a free tool will allow you to spy into the internal data of SharePoint and compare the effects of making a change. SharePoint Spy also allows you to compare settings between sites, lists, views, etc helping you troubleshoot configurations.
SharePointSpy is a great tool for developers. I stays away from infrastructure, providing your deep info about sites, features, site definitions and etc., allowing to export different schemas xml. Really powerful tool for developers, who need deep dive inside SharePoint stuff.
SharePoint Spy fails on Windows Server 2008
Does NOT run on Sharepoint installations running on Windows Server 2008. Installation fails if it's not Windows Server 2003.