ADUC BulkAdmin is a powerful bulk import and modify tool with exchange, SID History and Home and Profile Directory support.

Any changes you make to your active directory can be rolled back from the event viewer. You can also create import or modify sheets and save them to txt for later processing.

It's a great utility when you're planning complex migrations, want to reorganize and clean up your Active Directory structure, or have to import or modify objects on a regular basis.