A look at a fantastic tool for data clean-up: Google Refine
This is a walk-through of a sample project using Google Refine - standardizing the names of cities of publication for books. (from the 260|a for all you library geeks out there) This also shows how to link or reconcile to Freebase to return linked data to your spreadsheet!
I may have just created the most boring presentation in the history of "Prezi", but if you ever have to deal with cleaning up messy inconsistent data in spreadsheets, you will thank me later! :) And here is a slightly updated version in SlideShare form: