If you've managed Active Directory (AD) for a while, you've probably run into these tools, but if you're new to AD, you might not have seen them. Check 'em out.
AdFind: Combine ldapsearch, search.vbs, ldp, dsquery, and dsget tools and you'll get some idea of what this command-line Active Directory query tool can do. Brought to you by the guy who put the Joe in joeware.net.
ADModify.NET: Microsoft Exchange and Active Directory admins use this tool to deal with bulk user attribute modifications. Available at CodePlex, Microsoft's open-source project-hosting Web site.Specops Password Policy and compares NetIQ’s Group Policy Administrator, NetPro’s GPOADmin, and ScriptLogic’s Active Administrator