Deduplicate function (prior to copy\move)

If I am consolidating information from a drive (or set of drives) to a new one an option for deduplication would be awesome.  (I'd guess this would be a lengthy process depending on the number of files) but I find myself in this situation at work a lot.  Users with data all over the network drives and needing to move information to a new place without moving 300+ copies of the same file...for 300,000 files.