We had the Power Commands for Visual Studio 2008 that add a context menu command that Removed Unused Usings and Sorted Usings for all files in a project/solution.
How to do the same in VS2010 since this plugin is incompatible?
For Visual Studio 2012 just download the "PowerCommands for Visual Studio" extension from the VS gallery to execute "Remove and Sort Usings" for a project or solution:
http://visualstudiogallery.msdn.microsoft.com/e5f41ad9-4edc-4912-bca3-91147db95b99?SRC=Featured