If you’re using more than one computer on your desk I strongly recommend you look at the Mouse without borders utility that came out of a Microsoft Garage project this year. With Mouse without borders you can just use one mouse and keyboard to control up to 4 Windows clients. Furthermore you can drag and drop files from one screen to the other, take screen captures or just copy and paste text.
Mouse without borders can be downloaded from here and the unofficial support page is here
Mouse without borders
Please also check out “ShareMouse” which supports drag & drop of *multiple files* and works cross-platform between Mac and Windows.
Demo video: http://demo.keyboard-and-mouse-sharing.com