Opportunity history reports: a simple, out of the box function, that can do quite a bit when it comes to tracking your data. Opportunity History Reports allow users to view how an Opportunity has changed over time, and by adding a few additional formula fields, can help make the report more robust and flexible. Add a few formula fields and you can easily access data, such as the current Stage, Amount, Probability %, Close Date, and Forecast Category.
Alternatively, if you aren’t interested in complicating your Opportunity pages, but still want these great features, just give the Users/Profiles Read access to the Data in the fields. Easy as pie!
-Ryan and the Salesforce Guys