Connect older Mac Pro (DVI) to newer Apple Display (Mini DisplayPort) I have an older Mac Pro with two DVI outputs. I have access to an Apple Display that has a Mini DisplayPort connector, which I'd like to use as a second monitor. Is there an adapter out there that will let me plug in this Apple Display to my Mac Pro? 

Basically, I'm looking for an adapter with a female Mini DisplayPort connector and a male DVI connector, which is the reverse of this adapter that Apple sells.
DVI port cannot output DisplayPort protocols so a simple and cheap adapter (eg the reverse of the one Apple sells as posted in your question) will not work.  The reverse does work (a DisplayPort can output DVI signals), hence the proliferation of cheap adaptors to do this.

A number of manufacturers have build adapter boxes to allow the conversion to occur (there is electronics in these boxes that modify the signal appropriately to ensure it gets output in the DisplayPort protocol).  They are however more expensive that "just a cable adapter".

eg of manufacturers/products include :
Gefen : http://www.amazon.com/Gefen-Mini-DisplayPort-Converter-EXT-DVI-2-MDP/dp/B002QPWBEK
Atlona - http://www.amazon.com/AT-DP400-Dual-MINI-DISPLAY-FORMAT-CONVERTER/dp/B003CWEXWO

Bear in mind that you may need a dual-link DVI adapter box if powering a large screen (eg a 30")